Hehe. You asked for screenshots, you got screenshots. Tons of 'em. Maybe too many. But I was just finding it too hard to explain myself, and I was sure I was leaving some things out. Most of you experienced guys probably know all this already, so don't waste your time waiting for these downloads. However, if you had a hard time understanding my words the first time around, you might want to load this up and go eat a sandwich or something. 7 graphics at 25K each downloaded at 3K/sec is about...oh hell, a couple minutes.

Regarding the placement of sentry guns, in these levels (2fort4 being the favored one) I have my favorites. Number one favorite place -- about 3/4 down the flag hallway (closer to the flag, in the dark part) on the side. I put it on the side to hide most of its silhouette. [See Fig 2] That way an attacker will peek in, not see any resistance, and then charge forward committing himself, only to receive a hearty welcoming fireworks show in the form of a flame spouting from the end of your sentry. In addition to this, when I'm waiting in the actual flag room (which I'm usually not, the engineer should be roaming, repairing armor and getting more cells and ammo for his sentry), I nose up all the way to the wall, with my face against it, then slide over until I can just see the doorway in the corner of the screen. This way, I present the smallest profile to the attacker who's just sliding past the doorway to make sure no one is waiting there for him and that no pipe bombs are scattered around the entrance. Killer combination, and advise your teammates to do the same. [Editor's note: I make it a rule not to place the sentry gun withing range of a grenade, otherwise they are too easily killed. The flag hallway is ideal placement.]

Second favorite place? In the 2nd floor room directly adjacent to the grid floor room which drops down just behind and below the sniper deck, facing towards the upper ammo room and the entrance to the winding stairs to the flag basement. This is a very high traffic area, providing a choke point for both the ramps and rocket jumping soldiers who jump up onto the sniper deck to run through the back way (blocks them from entering, see Fig e). This is also very easy to defend, for it is near the ammo room and therefore an also high concentration of friendlies. Why a sentry gun then? Because it is an often neglected spot to place a sentry, and usually catches enemies off guard to really soften them up for the basement defense. This room is not usually considered a strategic area, but it very well is. Additionally, enemies must run toward the sentry to get into the basement, effectively doubling the speed of the rockets and bullets. This is also vulnerable to attack from below through the grid floor; it would be wise to keep an eye out for demomen lobbing pipes or soldiers shooting rox up near the sentry, but an EMP grenade can usually take care of them rather well. Anyway, you're right by an ammo room, so rebuilding and repairing is not really a problem. Focus more on providing information for your teammates on incoming attackers who are entering the basement. There is a way to get around this sentry, but it is more roundabout -- jump down the elevator shaft directly into the basement. However, there is almost constant traffic here from respawning players, and it is rare when someone can sneak through unscathed. Usually only solitary attackers will use this venue -- it's too difficult to keep a large attack force together after having to run across that little catwalk which runs across the ramp room, and leaves them clumped up, ready to get blown away by a few rockets or grenades.

Miscellaneous TF tip #17: If you're on defense, pick a good hiding spot where enemies can't see you when they come rushing in (good example: the little nook to the left of the door to the basement, coming down from the twisting ramps, in 2fort4). Then, let them run past into the flag room, and toss in a couple EMPs, napalms, concussion, or nail grenades right before they grab the flag. Then stand in their way -- they'll be trapped between the grenades and you, and in the time they have to make a decision, either you or the grenades will gib 'em or get 'em very drunk. Of course, this won't work with custom servers that play footsteps when you run... :) This is a great tactic if you are the only one on defense -- you'll catch them when they think they're safe, and that's the best time. Odds are, you have a better chance of killing the guy when he has your back to you and has no way of knowing you're there. Likewise, when attacking, don't forget to check these spots so your enemies don't use your own strategy against you.

• Those two spots are really the only two where I place sentries, though it is sometimes useful to place one on the opposite side of the fort, near the bridge, at the base of the battlement and between the two entrance ramps of the enemy fort. This way enemies jumping from above or leaving through the ramps get caught from behind, or a flag runner gets a bunch of rounds in the face. Often, if I hear that the flag has been taken, I will demolish my sentry and build one in this spot to catch the guy running the flag if I can get there quick enough. I usually can't upgrade it, though, so the merits of this are limited. Useful as a last ditch effort, or against a solitary runner such as a scout which no one can catch easily. [See fig 4, heavy type]
  • A variation on this is to have two engineers build a sentry gun on the area between the short ramp to the area under the enemy battlement and the bridge. [See fig 4, with the light type] This way, any snipers leaning over the edge will have some serious problems to deal with. A fully upgraded sentry will also catch enemies in the air which try to jump over the sentry, at least if you put them back far enough. The only disadvantage to this, according to and email from [REC]r3ptile-EG, is that enemies can lob grenades up from the water to destroy the sentry. However, you will have done serious damage to their points and morale. I guarantee you you will get a lot of hate messages about this position!
• I almost never build in the ramp rooms. These are usually well guarded, and a sentry is way too vulnerable here. Everybody expects them, and more often than not they are immediately discovered and destroyed. Since they can't dodge, their value here is limited. In my opinion, human players can defend the ramps much better than a sentry can. Possible sentry positions are in fig 5 (I was too lazy to take a screenshot for SK and 2forts, haha) and my favorite ramp room position in fig 6.
• And hey, if you're going to build in a spot with a narrow passage, please leave room to pass through. It makes no sense to choke off the ability of your teammates to pass through, no matter how much it restricts enemy traffic (unless it's something like the example in fig 3, where only enemy traffic is restricted). You will be hindering rather than helping, and you will hear it from your teammates.
• Another place for sentries is in the room which joins the main upper room (connecting the upper ammo closet, the ramp room, the sniper deck, and the grate floor room) to the ramps to the basement, as seen in fig 7. This will eliminate any flag runners, if it's still working when your flag gets taken, hehe. This works much better in the blue fort, for this corner is much darker there. I usually switch between this position and the one blocking the grate room. They think they're safe, then....BOOM.

A couple last sentry placement tips: first, go to the tips page for a suggestion from one of our readers. Second, see Fig 8. The two doorways are to the flag (left) and respawn/elevator (right). My back is facing the ramp entrance to the basement. By positioning the sentry in this way, you have eliminated the possibility of a grenade killing it. Some engineers hide it around the corner to the right and point it towards the two doorways in the background; I prefer it this way because it will catch anyone who comes through the door, and won't allow any attackers to get close enough to throw an accurate grenade. Additionally, it will pick up on any enemies which jump down the elevator shaft and enter through the back way; if they shoot at it, they are in the gun's detection range and it will shoot them. It will also be a big pain in the ass (pun intended) for any flag runners. Here, the sentry has no weakness other than being swamped with targets. :) Unfortunately, this is often all it takes to destroy a sentry; it's so confused it picks up on only one and then the others can destroy it while it's shooting at the target. Be sure to warn your teammates of its location so they can stay out of its way and let it do its job.

UPDATE 12/8

I got this tip from a friend of mine quite a while ago and only recently dug it up. This is a great sentry spot which is almost indestructable in the map 2fort32, which I don't play much anymore. I thought it would be something to put up, though, since this is the ultimate Engineer guide. :) Anyway, in the figure at right [fig 9] you'll see where this spot is. It's kind of hard to get to, but a simple grenade jump will secure your team's base against everything but rocket and pipe jumpers. Enemies will HATE you for this one.

• So, to sum up sentry placement, there are three key things to remember: keep it hidden in the dark, preferably in a rarely used spot, and with a low profile; always, always place him in a choke point (where several traffic areas meet, and there is no way around it); keep it in long hallways and away from short corners for easy enemy access; and don't place sentries in places that are more easily guarded by human players. Above all, though, remember that your sentry gun provides a valuable service of drastically injuring or killing incoming attackers, so place your gun in a place where it can do the most damage. Usually this must be accomplished by getting the enemy to commit to his path; you do this by placing the sentry at the end of a long hallway where the enemy will run in, be attacked, and then not have enough time to retreat. The delay on the lock on the gun will aid this. Do not forget the sentry is your most valuable tool, and bad placement will render it virtually useless.