Engineer strategy

From TF2 Wiki

The Engineer is the one of the most versatile classes. He can get his friends to the front line faster with teleporters, create a powerful sentry nest to ward off enemies from entering and can build dispensers to heal and supply ammo. His low health and standard weapons make him only good for quick assaults to weaken the enemy or to lure them into a sentry trap.

General

Help your fellow Engineers out by wrenching friendly buildings you pass by to keep them repaired. Also, help a new Sentry gun upgrade quicker if your Metal supply is high.

If the enemy takes out the Sentry gun of both you and your team-mate, consider rebuilding one gun at a time, to get it to the highest level faster in your time of need. A level 3 sentry is much better than two level ones.

Building yourself into a corner (with a Sentry and Dispenser on either side) may help protect you from backstabs and sapping, since the Spy has to jump both onto the dispenser and you to get the back stab you, and with you swinging your wrench, you are spy safe. The same thing cannot be said about sticky bombs however.

You can rotate the placement of a building while the blueprint is out by clicking the secondary fire button (default is right click). Changing a Sentry gun's direction allows you to place them in corners and other odd spots. Rotating a Teleporter exit affects the direction one faces when exiting - an arrow on the blueprint indicates the direction. Rotating a Dispenser has no effect on its function, but can allow you to cram it into a tight spot.

Striking placed buildings with the Wrench will cause them to build twice as fast as leaving them alone. This effect stacks with each additional engineer striking the building with their Wrench during construction.

Crouching (default: CTRL) after jumping will allow you to stand on your buildings.

If you're planning on building a Sentry gun in a forward area, consider building a Dispenser first, to supply you with Metal to upgrade the Sentry gun.

If the game goes to Sudden death mode, build a Dispenser first to provide health for your team-mates and Metal for yourself.

Don't build turrets facing into hallways unless you have cover from your team-mates, as your enemies will see them ahead and have a chance to fire ranged explosive weapons (Rockets and Grenades being the most commonly used). Build them in the corners just outside the hallway, attempting to avoid places where Demomen can easily bounce grenades at your Sentry gun.

Be careful standing in front of your Sentry gun. If an enemy runs past and you get caught between the Sentry gun and the enemy, your gun will fire at you; causing damage and possibly death.

Disguised Spies cannot walk through opposing Sentry guns and Dispensers. You can use this for Spy checking by placing these buildings in chokepoints, such as doors and hallways. You'll know a disguised Spy if he jumps on top of these buildings when obstructed.

Build a Teleporter entrance outside the Respawn area, and a Teleporter exit at a location of interest. For the defensively-minded Engineer, Intelligence rooms and Control points are desirable (but be careful with building teleporters that lead into your own key areas, as enemy spies can now use them to gain access.) Nothing beats a forward exit deep inside the enemy territory. Care should be observed when placing your Teleporter; plant the entrances in obvious, but considerate places (do not place teleporters on the stairs, as under-fire team-mates rushing back for health may get caught on them).

Hiding your teleporter exits (such as underwater) can help to make sure it is not destroyed. Just make sure your teammates know where it goes, you do not want them to get lost.

Take the time after building Teleporters to inform your team of their position. Most players don't use them if they don't immediately see them, so make sure they know that one is around the corner.

In points with small, one-person doorways (such as the left-hand room in the small building facing the BLU spawn on Dustbowl, or the balcony on the building near the middle point in Badlands) it can be wise to set up a Dispenser in the doorway. Though you are boxing yourself in, placing a dispenser in the doorway keeps Spies out, as they can't pass through dispensers either. Team-mates, however, can get through the dispenser. They'll have a hard time sapping the dispenser with you on the other end and more importantly, they can't get to your Sentry, which, in either of the two examples, is in a great position to help your team.

Consider moving your Sentry gun frequently, especially if you are not the only engineer or if your enemies are adept at taking out Sentry guns. Placing them in odd places that still overlook essential passageways will make your enemies paranoid as they will have to advance through your base carefully, even if they do not see your Sentry in its normal spot.

If an enemy Demoman is shooting Sticky bombs at or near your Sentry gun, consider trying to shoot as many of them away as possible with the Shotgun. This may get enough grenades out of the way of your Sentry that it will not be destroyed when the Demoman triggers them, or may buy your team-mates enough time to take care of the Demoman for you. Note that this strategy is rather risky and may result in death. Another option is to attempt at taking on the Demoman with your shotgun (or getting a teammate to do it) the moment he comes into sight - if the Demoman dies, all his stickies are removed with no damage done.

If their are holes in the ceilings, try to build a sentry in a way that it can look down these holes. It gets some funny kills since most of the enemies won't be looking up for a sentry.

When an enemy is on your tail and if you built a sentry nearby, play cat and mouse and lead your pursuer to your sentry gun. Just try not to die along the way and your sentry can kill the "cat".

If you build a dispenser behind you, and a Sentry in front of you, do NOT stand in between them. This will make it easy for a Spy to go ahead and uncloak/remove a disguise behind your dispenser, which will make the sentry turn around, kill you in the crossfire, but the dispenser then blocks the bullets/rockets from hitting him. He can then disguise himself and sap them, or wait for them to run out of ammo, and do an embarrassing knife kill on a sentry.

If you're fighting an enemy, and you're in a spot of bother, consider popping a sentry down in front of him. This wastes a valuable few seconds, but it can signal your survival, as your enemy has the tough decision of trying to finish you off before the sentry is built, or destroying the sentry, but wasting time in doing so. NOT recommended when fighting Pyros or Heavies, as they can usually destroy the sentry before you can even switch your weapons back.

Offense

It may seem a disadvantage having an Engineer on your team depriving you of an offensive class, particularly on Control point maps. This is not the case, however, as the Engineer can be extremely useful on the front line. As mentioned elsewhere, Dispensers are important to save a long trip to the supply room and a Teleporter can save slower classed team-mates a lot of time getting back to the front line after being killed. As of the December 11 update, one Level Three Teleporter effectively has the efficiency of five of default, Level One Teleporters.

Another technique is to choose an approach and set a Sentry gun on your way in, you then switch to the Shotgun and start blasting to distract from its build time, when things get tough run away towards your Sentry gun (hopefully it has survived, but listen for the 'Sentry down' sound to be sure) and the Sentry will take care of your pursuers. In effect this gives you an extra player while assaulting any position. Placing a Sentry gun while on the run takes practice as does getting a reasonable placement that will actually take down a few opponents before its destruction. This also combats the tendency for Engineer-heavy teams to start Turtling.

Setting up a mini-base with a Teleporter, a Dispenser and a Sentry near the front lines after capturing an initial control point can help your team maintain their position. A skilled enemy team can push you right back to your first spawn, forcing you to gain ground again even if you have already captured the first point.

Being Sapped

You can "bait" an enemy Spy by leaving a Teleporter on the way to your position. If the area is quiet, only few Spies will resist sapping it, which will alert you immediately that a Spy is coming. Another useful effect of this is that you can tell when an enemy is approaching and gauge their class based on the weapon icon shown at the top right of your screen in your building's death-message.

By that same token, placing a teleporter exit on narrow stairways, such as those behind the main spawn rooms in 2fort, will prevent cloaked spies from freely running up them, requiring a crouch jump to get over and wasting their time as the cloak runs down. This will, however, also obstruct your team-mates.

As an extension to the above, if there's little need for your Teleporters in a map, place them both around your sentry to stall a Spy briefly, as inexperienced players will sap everything in sight. The extra second could be the difference between saving your Sentry or not, and it will also help you identify the Spy.

It generally takes two swings of the wrench to remove a sapper. Most of the time, you should save your Dispenser first, as it will break from a Sapper faster than an upgraded Sentry, and regenerating its Metal supply takes a lot of time. If you are staying in the same spot, saving your Dispenser first will always allow you to rebuild much faster because you'll have more metal available. However, if the Spy has removed his disguise nearby, or there's urgent need for offense, you should save your Sentry first.

Weapon Specific

Shotgun

The Shotgun will always work in narrow corridors, such as the hallways in 2fort. If you're intending to babysit your Sentry Gun, like most Engineers do, make sure to build it in a spot where you can bottleneck enemy players. You will be able fight on more even ground now that the sentry gun has softened them up for a shotgun blast.

Pistol

While the pistol may seem innocuous in comparison to its bigger brothers, the shotgun and sentry gun, there are many situations where it will be a much more useful weapon. Shot-for-shot, the pistol will mostly outdo the shotgun in accuracy and damage at long range. If you couple this with your 200 rounds of spare ammunition and a dispenser, it is possible to ward off distant enemies. Pistol Spam can also be used for Spy-checking down narrow corridors, such as the long tunnel in Dustbowl 2.B. Take advantage of the critical hits since they can rack up damage quickly at approximately 45 health per hit.

Wrench

When a Spy is repeatedly sapping your sentry in an attempt to destroy it, your Wrench serves two purposes. First, you can use it to swing at the opposing Spy (2-3 hits is enough to kill one, not including Critical Hits). After that you can quickly turn around (while the Spy is backing off) and repair your Sentry. Two strikes from the wrench will disable a Sapper and halt the progressive damage it causes; you can then fully repair the sentry after the spy is killed. A good strategy would be to hit the sentry a single time, and then change targets towards the Spy, kill him and then take off the sapper with another swing.

Building PDA

When you're being attacked and you have your PDA out, quickly pull out another weapon. Don't be caught by an enemy when using this or you're an easy kill. Remember to use the handy key (usually "Q" on the PC) to switch to your most recent weapon. There are two PDA's, the Building PDA and Demolish PDA (The Xbox 360 and PS3 versions do not have a separate Demolish PDA). If a player chooses to construct an available building from the Build PDA, the player model will then hold a toolbox, and the player will see a template on the ground in front of them showing the orientation of the chosen building. While the template is visible, right-clicking adjusts the building's orientation by 90 degrees anti-clockwise, left-clicking starts the build and "last weapon used" cancels the build.

Dispenser Placement

There are different strategies around placing Dispensers.

To assist the construction of a Sentry gun and other buildings. Unless you have a local supply of Metal, many times you will want to build a Dispenser before building a Sentry gun or Teleporter. Often a Dispenser is built so that the Engineer can Wrench his Sentry gun, repairing it from attacks, while the Dispenser provides him with Metal and slow healing. Since the Dispenser is solid to the Engineer that built it, careful placement of the Dispenser can also prevent or minimize displacement of the Engineer due to rocket or grenade explosions. This is especially effective during ÜberCharge rushes when keeping the Sentry gun up is crucial. If you are expecting incoming fire, such as from Scouts, build a Sentry gun first and use the dropped ammunition from the Scout to build a Dispenser afterwards.
To slow enemy traffic. Members of the opposing team can't walk through your buildings so Dispensers can be strategically used to jam up doorways and stairs. (Hallways as well, to a lesser extent, but doorways usually won't have the clearance to crouch jump over them.) For example, a Dispenser built in the doorway to the top of the spiral stairs in 2fort can prevent a Scout from speeding by a Sentry in the area. Temporary Dispensers are especially useful in cases such as around your dropped Intelligence. In some cases it can limit the quick pickup by a scout or Spy.
Spy checking. Because the Dispenser is solid to enemy players, any player (other than the Engineer that built it) seen jumping a Dispenser is a Spy. Building a Dispenser in a location solely to detect Spies is typically not recommended since it most likely can be more beneficial elsewhere.
To defend an area. Dispensers are useful in the (temporary) case of dropped Intelligence or around a Control point. It allows heavies and pyros to defend and spy check the area constantly with unlimited ammo (with the added bonus of slow healing).
To reach otherwise inaccessible areas. Dispensers can be built in certain areas to allow the Engineer to reach or build on a higher location. On Gravel Pit, a Dispenser can be built below the tunnel exits from Blue spawn so that the Engineer can climb up into the tunnel and build. On Gravel Pit, the Dispenser is the first in a sequence of buildings that can be built to reach the roof of Control point B. NOTE: Since the Engineer's buildings are only solid to him and not his team-mates, this only benefits the Engineer unless he builds a Teleporter to allow team-mates to also get to the area.
- In some places you can climb on top of your Dispenser select a Teleporter exit and jump up, placing the exit at the peak of your jump.

Other notes:

Dispensers can block your Sentry's line of sight, so try not to build them in front of your Sentry whenever possible.
You can use them as cover for your other buildings and yourself.

Teleporter Placement

The most important tip with teleporter placement is to inform your team where they are and where they go, especially if you have a mic!

There are a few places where you can place Teleporters that almost always go unnoticed. These places are:

On Dustbowl Stage 1 Cap 2, in the room with the grating.
On Dustbowl Stage 2 Cap 1, to the right as you enter the Capture Point A building.
On Dustbowl Stage 2 Cap 1, behind the office building.
On Dustbowl Stage 2 Cap 2, in the long tunnel with the grating.
On Dustbowl Stage 3 Cap 2, attackers need a Teleporter in the area before the long stretch to the Control point.
On CP_Well - in the water, on top of the enemies one-way exit pipe.
On CTF_2Fort - in the water, against the wall on the enemy side.
In the middle Sniper nest on CTF_2Fort. Most Snipers avoid this area due to its lack of cover. Getting up there in the first place is difficult of course.
Outside of the enemy base on 2fort, in one of the corners. Unless a firefight breaks out on their side of the map, most enemies don't bother checking these spots and walk on past.

You can also place your Teleporter as a decoy. For example, You can put a Teleporter at the top of the spiral in CTF_2Fort. When it's destroyed, you know an enemy is coming from that direction. This is called "spy bait".

Always build Teleporters at the start of a match, especially if you're defending. Build the entrance and then quickly go to the supply closet and head to the capture point 1 to build your exit. After these two have been placed, you can then go ahead and build your Dispenser and Sentry. Teleporters get your team to the front lines instantly; if you want someone watching your back, get those Teleporters up or your Sentry will not be covered by your team-mates. You will often need support while your sentry is setting up and while it's only at level 1.

Also remember that enemy players who walk over a teleport exit while you or your team-mate uses it will die (telefrag). This can occasionally be useful to kill disguised Spies who don't know this; once they learn about it, they then have to avoid the exit, being careful to jump over it, so the exit can be used as a somewhat less effective blocking construction.

Be sure not to stand on your own teleporter exit if you have set up a forward base; doing so may allow an enemy Spy to telefrag you, leaving your base defenseless against his sappers. If time and configuration permit, be ready to use your wrench on anybody who comes through your exit whenever you aren't tanking your Sentry.

On CTF maps, your team can benefit from teleporters providing a quick means of getting back to the spawn/supply rooms enabling those with low ammo/health to get back to the fight without a respawn penalty. However, a teleporter going from the spawn to the front line is generally more helpful to the team, so don't do this unless there are other Engineers with teleporters set up. Two engineers can provide a two way passage between the front and the resupply area. Upgrading multiple sentries with the advantage of the resupply room makes a big difference. Likewise any team-mates with low health and ammo can resupply and return quickly.

2Fort

Ideal places to put Teleporters while defending the Intelligence room are on the spiral stairs and the bottom of the long straight stairs, to warn of incoming enemies and bait enemy Spies.

Sentry Placement

There are three types of Sentry placements - the bad ones, the decent ones, and then there are the ones that win games. Below is a list of 'game winning' Sentry placements. Note that there are many more Sentry locations that are 'good' or 'decent', but the ones listed here are typically very hard to destroy.

General Strategies

As a rule, do not camp behind your Sentry and crouch all the time. Only do this when it is actually under attack. The reasoning behind this is that all a Spy has do to is come in under his cloak, jump onto your head where you cannot see him, decloak. From here, he can stab you and sap all of your buildings. If he stabs you while he is above you, it counts as a backstab. It takes practice to do this, so follow this rule as other player's skill allow. But beware of this tactic as it can reduce all of your buildings to rubble very quickly.
Team up. During set up time a pair (or more) of engineers can quickly get a single sentry gun up to level two or three before the opposition leave their base. One level three Sentry is much harder to take down than two level ones. During Set-Up phase on Gravel Pit you can assist a friendly engineer to build a teleporter exit and maybe even a sentry inside the tunnels in front of the BLU spawn door.
One engineer can babysit the gun of more than one engineer leaving them free to set up teleporters and dispensers on other areas.
During setup time, the whole team can spawn as engineers and help build the structures of team members who will remain as engineers while they respawn as other classes in the spawn room. If, rather than returning to their spawn room, the other players suicide before switching classes, this will have the added advantage of providing additional Metal for the remaining engineers, though also slowing their return to the front lines due to respawn delays.
If there are buildings just outside your spawn room, you can switch to engineer, use your starting 200 metal to upgrade something, then return to the spawn room and either become your playing class or switch to something else, then back to engineer and repeat the process.

CTF_2Fort

On the ledge in the ramp room. It is important to place it no further out that the middle of the ledge (if you place it at the corner the Sentry can be shot from the battlements without triggering it) and as close to the edge as possible, not at the corner, otherwise it cannot see down to the ground to fire upon incoming hostiles. By being up on the ledge, you cover the entire room, and there is only one way to destroy it without putting the attacker in range of the Sentry. To destroy it, the attacker must come up from under it, and splash damage it from below, or clip the corner of the Sentry with their weapon. If the Sentry is placed at the junction of the right side ramp and the top ramp, then it blocks the movement of enemy Spies into the hay room and has a shorter arc to turn in, to lock onto enemies.
- Note: On the Xbox 360 and PS3 version, Soldiers can use their rockets from below to damage the Sentry gun on top. This is an exploit, although it still must be warned against as many a Soldier who knows the Sentry Gun's position can simply blow it up from the bottom of the ramp room.

Across from the Respawn area in the corner of the hay room. Place a Dispenser in the corner against the wall separating the grate doorway and the room. Then place the Sentry against the wall (use right click) by the Dispenser facing the doorway to the spiral. This Sentry covers the grate and battlements, which if the previous Sentry was placed, not only protects the hay room, but also prevents access to the only other entrance to the intel.

In front of the fire extingusher on the spiral. This is very important if you want to elimnate Scouts coming from the second floor trying to grab the intelligence that use the Spiral. Since your placing the Sentry in front of the fire extingusher, this is the mid point of the Spiral. So this spot isn't visible from the entrance of the Spiral. Build a Dispenser sideways on either side, then place the Sentry in front of the fire extingusher wall. This is a uncommon yet good way of taking out opposing Scouts. Soliders and Demoman who rocket/stickey jump to the top floor and enter from the Spiral will also be suprised.

The 'mid' point in the sewers. It's very important that you build it facing the short pipe, and not the long stretch. Don't build it in the corner facing both pipes (it can be splash damaged there). Instead you want to build a Dispenser against the wall in the corner (facing the long pipe) and then build the Sentry in front of the Dispenser (angled so it is facing the short pipe). What you end up with is a Dispenser flat against the wall with the long pipe in it, and the Sentry up against the Dispenser, but facing the short pipe. There is no way to get enough splash damage on the Sentry from this position to blow it up easily, and it locks down the sewers. This can also be used offensively by building it in the enemy base. Of course, you must still watch out for Spies, who over such a short distance will be fully cloaked and be able to come right up to you before decloaking. If your back is visible, they will be able to backstab you with surprise. The Sentry will then kill them, but without its Engineer, it is much more vulnerable.

In your Intelligence room, in the 'short' corner (the corner between the two doorways). The placement of this Sentry is very tricky to get perfect, but if you do, it's very hard to take down. To place this Sentry correct you should to put it as far into the corner as possible (use right click) and at a 45 degree angle. Next you want to place your Dispenser in front of the Sentry, but rotate it so that the short side of the Dispenser is what block's the Sentry's field of view. The Dispenser should be placed just off center, so as to not block the line of sight to the Intelligence or either doorway. An alternative is to place the Dispenser out of sight behind the desk it is much more vulnerable but often goes unnoticed.

Under the enemy grate. This is a very unlikely position to attain and hold. However, if you can get a gun built here, it is possible to jump onto your gun and then jump up to place a teleporter exit on their grate. If you end up in a game where the enemy is turtling in their ramp room but otherwise letting you walki in their front door, you could utilize this strategy to surprise them.

CP_GravelPit

Control point A
- Just in front of the little hut to the right (if you're facing the BLU Respawn area) of the point. You should aim it so that it faces the edge of the map, and thus pans from the point to the start of the hill. The advantage of putting a Sentry here is that it's very hard to hit with splash damage because it's uphill. You can also put your Sentry in the hut. The only way to take it out is by using a Demoman (or a skilled soldier), or ranging it from the C side of the point, and this is where the next Sentry comes into play.
- The left (if you're facing the BLU Respawn area) corner of the Control point. You should build it just outside of the Control point, but with the Sentry's back to the Control point (just before the corner of the Control point). The sole purpose of this Sentry is to cover the previous Sentry. You should build it so that you can stand inside the relative comfort of the Control point and still be able to heal the Sentry. This also protects the Sentry from splash damage. Note that this one has a slight weakness to the ramp entrance of the Control point due to the tracking time required to shoot from that direction.
- On defense, build a Dispenser along the wall where the tunnel from the attacking team comes from. You should be able to jump, crouch, jump, crouch into the tunnel normally only accessible by the other team. Once the Dispenser begins building itself, you should rather find a small Ammo pack for just enough Metal for a Sentry. Four Engineers would just about completely halt the other team. Experienced enemy Spies would be able to sneak around and still cap spots if team-mates don't defend there. Well-placed, or lucky if you built your Sentry in a good position, grenades and Sticky bombs from a Demoman would cripple the Sentry in a short while. Heavies or Soldiers with Medics would dramatically hurt here as well.

Capture point B
- Behind the rocks by the left BLU Respawn area, facing directly away from the Respawn. By putting a Dispenser against the rocks, and then placing the Sentry against the Dispenser, you create an encampment that covers from the left side of the rocks, to the entrance of Capture point B. The rocks protect it from attacks from the Respawn area, and the angles make it hard to hit from the right point without being in range (though it is possible).
- Under the left stairs leading from Capture point C to Capture point B (facing the way to Capture point C). Don't build it right against the wall, but rather build it such that the Sentry is pointing to the back entrance of Capture point B (with line of sight), and so that you can hide under the ramp with a Dispenser and repair it.

Point C
- On either ramp leading up to the tower (the big metal ones). The trick to making this Sentry deadly is in its position. You want it facing the tower, and back against the rock wall (use right click, and the Sentry should be at roughly a 45 degree angle). You also want to put it about 2/3rds of the way up the ramp, not at the top of the ramp. The idea is to build it such that when it's fully upgraded only the guns and Rocket launcher are visible. This allows the Sentry to attack, but minimizes what is visible (due to the height difference, and the little wall at the entrance from Capture point B). One of these on each ramp, blocks all access to the tower, and can even hit people at the top.
- On either of the second landings of the tower (in the corners). The ramps up to the 3rd landing protect it from the middle entrance to Capture point C, and it's in range to attack most people from the side entrances (except Soldiers). As long as you sit there and spam repair the Sentry, it should stay up with anything less than two Soldier's hitting it (or one Soldier who gets a pair of Critical hit Rocket's).

CP_Well

In the rafters over the first Control point. This is by far the longest set up, but if you get a Teleporter into the rafters, they'll have one hell of a time getting that first Control point. There are two ways of doing this:-
1. Jump in front of the cabinet on the second level (right side) and drop a Teleporter exit on top of it. Next build your Sentry on top of the cabinet, just before the rafters, then jump up.
2. Alternatively jump onto the trolley at the side of the cabinet on the second level (right side) and then up on the cabinet (you have to get timing right and make sure you're on the left side of the trolley). Next build your Sentry on top of the cabinet against the wall, just under the ledge. Jump on top of the Sentry and then onto the ledge.

Once you're up there, rebuild the Teleporter exit so you don't have to go through that procedure again. If you build the Teleporter exit all the way in the corner, it's not visible and almost impossible to destroy (barring the Demoman's Sticky bombs, but he will have to know exactly where it is). From here, you have several good Sentry positions. Just watch the line of sight to the Sentry, and just about everything is a good spot.

Note that some people consider this an exploit.

On the little catwalks on either side of the second Control point. Build the Sentry in the corners further away from the point (where the Health pack spawns). If you build them close to the Control point, a Demoman or Soldier can splash damage them. By building them on the side of the opening further away from the Control point, you not only gain more attack area inside the Control point, but also cover it from most splash damage.

Behind the first set of boxcars (between Control point 3 and Control point 2). If you build the Sentry about half way down the boxcar, it can't be splash damaged unless a Soldier Rocket jumps over the boxcar, or a Demoman throws grenades at it. This one works wonders as an Offensive Sentry as well.

Against the wall facing Control point 3, in the enemies Sniper nest. Why the other team? Because it will take them longer to notice, and it's very unlikely that they'll come from your side when attacking the Control point. They'll either be jumping or Rocket jumping up to the Sniper nest (which is covered by the Sentry), or coming up the closer ramps (also covered by the Sentry. Just make sure it's all the way against the wall, and in front of the doorway (use your secondary attack to rotate it).

TC_Hydro

TC_Hydro, due to its changing nature and layout, has no 'perfect' Sentry locations. There are however, a few very good ones, which are listed below:-

On the metal landing at the flooded Control point (the one with the Control point on the raised area, with water all around).
Behind the truck at the outside Control point (the one with the raised Control point on the little bridge).
Under the stairs at the radar dish.
At the end of the raised platform at the Control point inside the base.
Under the Control point inside the base, at the back on the ground floor where the turbines are. If you position the Sentry on the corner of the alcove and a Dispenser behind you, you will be saved from most of the splash damage while using the Metal from your Dispenser to repair your Sentry. You wouldn't think it but the Sentry range does cover the Control point and the stairs. This is quite difficult for the enemy to take down if someone is covering you from the top rails, if they aren't, a Demoman or Soldier can take it out from above.

CP_DustBowl

At Stage 1 - Point A, you can build a Sentry on the little landing inside the Control point. The only way to destroy this Sentry is to come from the mines, or with Sticky bombs.

Also at Stage 1, but this time by the BLU Respawn area (same side as the Control point). You can build a Sentry on the back side of the little hut (facing the trench) and have it cover both the right (if you're facing BLU's Respawn area) and center entrances'.

At Stage 1 - Point B, if you build a Sentry to the left (if facing the point) of the Control point, you can cover both the stairs, and the Control point while being very hard to splash damage.

Also at Stage 1 - Point B inside the mine room, next to the one-way door. This will cut off two access routes for the enemy, and because of the Health that spawns, you'll be very hard to kill.

When attacking Stage 2 Point A, put a Sentry in the dugout area. This will prevent enemy Pyros and other classes from rushing in and spawn camping.

When defending Stage 2 Point A, put a Sentry nest on top of the Large Shed. Have another Engineer build a Dispenser up there to make it so you always have enough Metal for repairs. Build a Dispenser next to the ladder and have a Pyro stand next to it, constantly flaming the ladder. This will prevent enemy Spies from coming up there and sapping the nest.

Stage 2 - Point A - Build a Sentry on the house to the left of the BLU Respawn area. While not invincible, it's a very hard spot and attack from the BLU Respawn area.

Build a Sentry inside the Control point building on the second floor, but under the roof, at a spot where it can see both the stairs and the outside.

Build a Sentry at the Control point building in front of the narrow hallway leading to the BLU Respawn area.

Stage 2 - Point B - On the ground, facing the Control point in the left (if facing the BLU Respawn area) corner. It covers the Control point, and is hard to take out from most paths (the exception being the long path by the rocks).

When Attacking Dustbowl Stage 3 Cap 1, build a Dispenser and Sentry right in between the two double grating doors. This will prevent enemies from attacking and will help refuel your allies who've been wounded.

When defending Dustbowl Stage 3 Cap 1, build a Dispenser and Sentry on the loading docks. The Sentry will pin down the enemies coming through the double grating doors.

Stage 3 - Point A - From RED Respawn area, there is a path that leads to an opening overlooking the first Control point, by building a Sentry here, and a Dispenser behind you, you can wedge yourself far enough back to not be hit by splash damage, but still repair the Sentry. The only way to take this Sentry out is with a Demoman, or multiple Soldiers.

CP_Granary

Due to the layout of Granary, there are fewer 'good' Sentry placements. The few that are very good are:-.

On the balcony of the Control point 2.
By the machinery at the Control point 2.
On the containers at the Control point 3.
Under the ramp/pipe at the Control point 1.

When placing Sentry Guns on the containers at Control point 3, try to place it so that the gun can fire into the door at the top of the enemies' ramp room. This way, Soldiers cannot use this as cover to dodge in and out of to get a straight shot on your gun. This also covers both entryways, and makes it hard to splash damage without getting right underneath it.