The Sentry Gun is an upgradable building in the Team Fortress series. It can only be placed by Engineers. It costs 130 units of Metal to build and uses Shells (and Rockets at level 3) for ammo. It can be upgraded twice after being built (except for the Mini-Sentry).
When a Sentry is being built, the player will be unable to move. If the player is killed while the Sentry is under construction, the Sentry will disappear.
Something to note is that fire from a Sentry Gun, even at its lowest level, will push enemies back until they either find cover or are killed. This proves useful in keeping enemies away from an Objective.
In ETF, a Sentry has a camera that appears on the bottom-left-hand corner of the screen. This camera shows what is directly in front of the Sentry. The less health the Sentry has, the more static that will be on the camera screen.
- Place your Sentry at chokepoints, such as the entrance to the ramp room in 2fort, the entrance to the security room in Shutdown2 and the entrance to the key room in Rock2. However, remember that Sentries are not invincible and will be destroyed, even if you put it in the world's best spot.
- On that note, don't try to invest more (physically and emotionally) than what is needed for your Sentry. Consider Sentries as disposable; that way, you can easily build a new one if the old one gets destroyed.
- The Sentry will do the same amount of damage, no matter what level. The major differences between levels is the rate of fire and extra health.
- When you replenish a Sentry that does not have maximum ammo, it will take 40 Shells (and 10 Rockets, if at level 3). If you have 50 Shells, keep the extra 10 Shells that you have after refilling the Sentry; 10 Shells might make the difference between life and death if an enemy attacks while you're running to get more ammo.
- If your Sentry is destroyed, it is highly recommended that you do not build another one in the same area, as enemies are sure to find it.
- When your Sentry is under attack, wait until its health is low, then repair it. This helps conserve Metal. The only time when you should be doing the opposite is when you're 'Sentry Tanking'.
- If you're building a Sentry in an area that is frequently attacked by enemies, consider priming a Grenade before you build. That way, you can attack anyone that is trying to kill you while you're building.
Level 1 Edit
At level 1, the Sentry is equipped with a single-barrel Machine Gun. It can hold 200 Shells and has an average amount of health. It takes 30 Metal to repair the Sentry from 0% to 100%.
The level 1 Sentry is very strong. It can get many kills, but only if enemies are unaware of the Sentry. Its fast firing rate makes it easy to for it to kill a strong class, such as a Soldier or Heavy without assistance. It should be upgraded later.
Level 2 Edit
The level 2 Sentry is much more powerful than the level 1 variant. Upgrading to level 2 gives the Sentry a much faster firing rate than the level 1 Sentry and greatly increases its health. A Sentry should be upgraded to level 2 as soon as possible, because of how much better it is than the level 1 Sentry. In fact, if you are torn between upgrading your level 2 Sentry to level 3 or upgrading an ally's level 1 to level 2, you should upgrade the ally's. Two level 2 Sentries are more effective than a level 3 and a level 1.
Level 3 Edit
At level 3, a Sentry gains two Rocket Launchers (a single, 4-barreled Rocket Launcher in the TF2 version) and more health. It takes 43 Metal to repair a level 3 Sentry from 0% to 100%.
Despite its impressive weaponry, the level 3 Sentry isn't much better than the level 2 Sentry. Its rockets are slow enough that most classes can evade the rockets without breaking a sweat, and it has the same firing rate that the level 2 Sentry has. What makes it useful is that it gives the Sentry a decent chunk of extra health, which can be a lifesaver in some situations. However, there is no need to upgrade to this level right away, so don't worry about upgrading it while your base is under attack; instead, keep repairing the Sentry while enemies come in, then upgrade it when there's a lull in enemy attacks.
Caring For Your Sentry Edit
Just because a Sentry can fire a weapon autonomously doesn't mean you should 'set it and forget it'. Many overeager Engineers, not content to 'babysit' their Sentry, have walked away to work on another project, only to hear the alerts of their Sentry under attack. Sentries must be kept under a careful watch, lest they fall victim to Soldiers, Spies, and other attackers.
- The first key in keeping a Sentry safe is to keep it secluded. Rotate it a half turn and back it into a corner when building it, and make sure that it can't be spotted outside of its sensor range. This makes your Sentry much less vulnerable to enemy fire.
- Watch out for Spies trying to do "hit and runs" on your Sentry. If you see an ally shooting out a lot of Frag Grenades at your Sentry, that's actually a Spy trying to destroy your Sentry! Try to distract him long enough so that he can't destroy the Sentry.
- When taking care of or building your Sentry, don't be surprised if you get backstabbed. Many Spies can't resist backstabbing an Engineer that's preoccupied with taking care of his Sentry.
- If you see either a Nail Grenade, a MIRV Grenade or a few Pipebombs near your Sentry, abandon ship! These will always destroy your Sentry, and you can't do anything to stop them from doing so. If you can, dismantle the Sentry so that you'll have enough Metal to rebuild it at another location.
- Ask friendly Engineers to occasionally check on your Sentry. If yours is under attack and you're too far away from it to repair it in time, then a friendly Engineer is the only person that can repair it for you.
- In ETF, remember to keep an eye on the camera! If a Spy tries to hit and run it, then you'll usually be able to see what the Spy's disguise is via the camera before the Sentry is destroyed. This allows you to alert your teammates so that they'll be ready to take down the Spy when they see him.
- Also in ETF, beware of enemy Spies trying to sabotage your Sentry! If you see an ally that is standing too close to your Sentry, begin attacking him! A mixture of Railgun and Super Shotguns rounds will kill any Spy attempting to sabotage your Sentry.
- In TF2, Spies have Electro-Sappers. Sappers will attach on your Sentry, disable its ability to shoot and slowly damage it until it breaks. Remove it with your Wrench, but watch out for the Spy who placed the Sapper, as he'll always be happy to backstab you while you are trying to remove it.
While the Sentry may seem unstoppable to beginners, it is pretty easy to destroy one if you know what to do. First off, a Nail or MIRV Grenade will destroy even a level 3 Sentry if the grenade lands near the Sentry. However, this strategy is only available to the Soldier, Demoman and Heavy, as only they have one of those grenades.
Pipebombs are also very effective against Sentries. Enemy Engineers cannot do anything to remove the grenades, so once they see a few pipes land near their grenade, all they can do is run. Grenade Launcher grenades can also destroy a Sentry, but only if it is unattended.
The Nailgun and Super Nailgun can destroy a sentry if it is unattended. To do this, get out of the Sentry's range, then open fire with the Nailgun. Because the Nailgun has perfect accuracy, your shots will always hit the Sentry. A few seconds of firing will destroy even a level 3 Sentry!
Dealing with Sentries as is easy as Spy Checking. Since Sentries cannot detect you because of your disguise, all you need to do is toss as many Frag Grenades as possible at it. Usually, about four (two in TFC) will destroy a level 3 Sentry. If a Sentry survives a grenade bombardment, you should begin shooting it with the Nailgun. While doing so will reveal your disguise and make you vulnerable to the Sentry, a Sentry that has survived four Frag Grenades is so weak at it only takes a few Nails to destroy it.
In ETF, Spies can sabotage a Sentry. When doing so, make sure that you're not near the front of the Sentry; otherwise, the Engineer that build it will see you sabotage it and will attempt to kill you. Also, remember not to attempt to sabotage while an enemy Engineer is nearby; he'll likely notice you attempting to sabotage the Sentry and will attack!
A level 1 Sentry is very easy to destroy if you are aware of it. About two (one in TFC) Frag Grenades or Rockets will completely destroy it. Even if you are within the Sentry's range, its slow firing rate will slowly chip off damage, giving you enough time to destroy it.