This guide will outline the trick of wall-clipping, which is an innate ability in the game, and, like the advanced alien maneuvers, is completely possible without anything external to the game itself, such as a mod or trainer. Wall-clipping is an exploit brought about by a strange function with the alien's crouch-jump mechanic and the construction of various walls in the game.

I recognize that there may be some controversy surrounding this guide. Please note that wall-clipping is not cheating, it is a function of the base game. It works in every version of this game released and can be performed regardless of whether or not external programs are being used. It does not require debug mode and works in both single-player and multiplayer modes. I do not endorse cheating of any kind in multiplayer. Whether or not wall-clipping is unfair is for the player to decide, but it has become clear to me that it is closer to being unfair if it is not made known publicly. Please don't send me messages or comment about how I'm breaking the game or supporting cheating, hacking, or exploits. For the first three, it's simply untrue, and for the last one, I feel that making people aware of its existence is better than pretending that it doesn't exist. I personally find wall-clipping fun and legitimate.

It should also be noted that while you can sort of make plans around wall-clipping, this feature is not reliably strategic. Aside from saving you time and possibly surprising a player, getting kills with this method alone is exceedingly rare. It usually makes you vulnerable to attack because the screen needs to take a second to reorient itself. The practical applications of this trick are usually saving time, escaping pursuit, taking a shortcut to an enemy if you know where he is, avoiding proxy mines, or, more often than not, simply amusement. Realistically, it usually takes too much time to set up and execute to save that much time, unless the normal path is being watched or being spammed with proxy mines.

The first section of this guide will explain how to perform the wall-clipping ability. The rest will consist of locations where it works in multiplayer maps. Note that I'm not concerned with single-player maps here. You can find plenty of places to clip through in the alien campaign on your own.

Clipping through walls and floors without an external program such as a trainer can only be done at specific places that meet a certain set of criteria, if you perform the move correctly (which is quite easy with some practice). The criteria are mostly clear. Here is how it works:

• You must be an alien. No other species to my knowledge can clip through walls.
  
• You must crouch-jump at the wall you want to clip through.
  
• You must let go of the crouch button before you pass through the wall.
  
• The wall must be of a particular thinness. Most walls are too thick to clip through.
  
• There must be an area on the other side of the wall for you to be in.
  
• You must not be too close to or too far away from the wall to which you're jumping.
  
• You typically have to be already attached to a surface using the wall-crawling (crouch) ability. Almost all clippable walls are floors, so you'll have to be attached to a ceiling before making the jump.

That's it, just crouch-jump as an alien through the wall you want to go through. Most walls can't be clipped through. There are even certain walls and floors that you can clip through in some places but not in others. Other walls that are unclippable could theoretically be clipped through if there were something on the other side. The above criteria are confirmed, but it is unknown if there are any more.

The best places to practice are the first location in the Statue section and the main floor in Office.

The following is a list of walls and floors where this trick works.

Location 1:
Where It Is: Second floor. In the screenshot, at the direct bottom is the window facing out over the staircase with the blue light leading down into the basement section. It's easiest to climb where the hazard strip starts and look straight down.
Where It Takes You: This takes you right to the foot of the stairs below. There's not much point to this spot because you could just jump out the window or leap down the stairs.

Location 2:
Where It Is: Second floor. This again is right next to a window overlooking a staircase. This is also one of the very short connecting passages between the center multi-tier section (with the flamethrower) and one of the hallways (seen on the right). As before, it's easiest to climb where the hazard strip starts and look straight down.
Where It Takes You: This again takes you to the foot of some stairs, though this time you'll be right next to some arches instead of just a middle of a corridor. Again there's not much real point to this.

Location 3:
Where It Is: This is the gray floor on the second floor with the healthkit in the room with the staircase on two walls. The entire floor is clippable here.
Where It Takes You: This takes you right into the main central area with the flamethrower. It's got great practical usage for surprise but ultimately leaves you exposed as you set up (unless you hang out on the ceiling). You can make it through the floor by climbing on different stairs and making the jump.

Location 4:
Where It Is: Third floor. This is the area at the top with the predator orb and marine pistol. The floor here is clippable from the top by the orb, though it doesn't quite go down all the way.
Where It Takes You: Onto the ledge below in the central multi-tier room, somewhat close to the SADAR. This one seems to have some strategic usage, though you could just as well fall out the window.

Location 1:
Where It Is: This is a small corner platform that holds the only SADAR in the map, nearby two staircases.
Where It Takes You: This takes you down a flight to the curved staircase above the two pistols that leads out to a main corridor section. This one seems pretty useless.

Location 2:
Where It Is: On the top floor, in the area between the smartgun and flamethrower.
Where It Takes You: This takes you to the easily wall-glided, curved, gray corridor immediately below, near a staircase and a side passage. This spot has more potential than the previous one.

Location 3:
Where It Is: On the top floor by the grated floor overlooking a multi-tiered vertical area of the map with the flashing light.
Where It Takes You: This takes you into the open room with the grenade launcher. This is probably the most useful of the three if you need to make a surprise attack in that room, though you could always just fall or wall-bounce into it, just the same.

Location 1:

Where It Is: This is the upper, darkened area where only the alien spawns. It doesn't always work but you can sometimes pull off clipping through the floor here by climbing onto the slightly lowered section.
Where It Takes You: Clipping through the floor simply takes you right onto the exposed, bright corridor next to the staircase beneath you. There's very little strategic use for this that I can tell.

Statue is one of the best maps for clippable walls. Many of them can be used strategically and unlike the more or less quirky uses of the previous levels' spots, here they actually add a new element for strategy.

Location 1:
Where It Is: The first raised platform with the orb, healthkit, and armor can be entirely clipped through. Simply climb onto the platform directly above it, look straight down, and jump. This is one of the best spots on which to practice wall-clipping.
Where It Takes You: It takes you straight through the platform and onto the central floor by the two pedestals, right in front of the dark blue corridor. While it's possible that a camping player may be looking out and spot you immediately, this is a good shortcut for getting into the middle of things because few marine and predator players will be looking up for you.

Location 2:
Where It Is: The next platform up (holding the SADAR) can also be clipped through, on either side of the columns or in between them.
Where It Takes You: This also takes you right into the central section and is better than the previous spot because you're entirely undetectable from the bottom floor, though it's also more difficult to pull off than the previous one.

Location 3:
Where It Is: Very near the last location, on the platform with the SADAR, is the giant alien neck and head peering out of the wall. If you climb directly onto the chin of the head itself, climb as far as you can go, and look toward the wall, you can actually pull off a jump through this wall.
Where It Takes You: This will take you into the largish central room with the minigun, skeeter, pulse rifles, and armor. This is a great shortcut if you can pull it off right because it means you won't have to travel as far up or equally as far down, saving whole seconds off your travel into the room.

Location 4:
Where It Is: At the ceiling of the main room with the platforms, right next to the hole that only the alien can reach, there is a curved section right across from the same wall that's clippable as the last location. Angle yourself on the curved section and jump through.
Where It Takes You: Like the last location, this takes you into the central room, although this time you'll be closer to the orb and skull of the xenomorph statue rather than the lower floor. This spot is considerably more difficult than the last to pull off.

Location 5:
Where It Is: Inside the central room itself with the alien torso, climb onto the neck of the xenomorph (the part jutting out through the wall), look down, and jump.
Where It Takes You: Into the heart of the bottom floor, by the medkit. This is probably the most useful location, possibly in the entire game, because it is right next to an alien spawn and takes you directly into the meat of things without useless wandering around corridors and falling down platforms. This definitely will save you seconds, even minutes of time, depending on how long the matches you play are.

Location 6:
Where It Is: Very near the previous location, this is again located in the bottom floor of the central section with the torso of the alien statue. Climb the torso from the bottom section but this time stick closer to the grey wall. You can clip through a small section of the floor here, too.
Where It Takes You: This also takes you to the bottom floor of the map. It's not as viable as the previous example to use, as it's trickier to angle yourself correctly.

Location 7:
Where It Is: On the first platform in the arena section where the first set of stairs lead out, by the armor. Climb to ceiling, look down, and angle yourself into the corner as you jump.
Where It Takes You: This takes you straight below to the area where the staircase corridor overlooks.

Location 8:
Where It Is: On the opposite side of the previous location, by the pulse grenade pickup.
Where It Takes You: This again takes you straight below, near the staircase corridor.

There are no known clippable walls in Jockey.

Location 1:
Where It Is: In the central orangish room with the minigun and staircases, on one of the segments with a camera looking toward the stairs.
Where It Takes You: Just beneath the staircase by the minigun. This can potentially be handy against camping minigunners.

Location 2:
Where It Is: In the grenade launcher corridor next to the hole in the floor.
Where It Takes You: It simply takes you into the corridor below it, just the same as if you had fallen down the hole.

Location 3:
Where It Is: In the horizontal corridor with the orb leading out toward the central room. This segment is very difficult to clip through.
Where It Takes You: It takes you to the corridor below. This can potentially be handy against marines but it's difficult to pull off and you're very exposed to the open central section preparing for this jump.

Hadley's Hope has a ton of clippable floors. Most of them take you to the basement section. These spots can be used more strategically than in most maps, though not as strategically as in Statue.

Location 1:
Where It Is: The first location, despite using four pictures, is simply the upper vent section with the acid hole on one end. The majority of this floor can be clipped through, the only problem being when you get to the junction of the third side passage. The first second and second are completely clippable.
Where It Takes You: Clipping through this vent floor lands you onto the grated floor that comprises one of the two framing sections of the main floor. This is the section that leads from the acid hole in the floor to the other side with the hole in the floor (with the flashing light). This can potentially be used strategically because every alien spawn point is in the upper vent section.

Location 2:
Where It Is: In the room with the smartgun and predator orb, a narrow segment between the healthkit and the wall can be clipped through.
Where It Takes You: This takes you into the basement area. It can be handy because from this point the only way down is in one of the main corridors, which can be deathtraps.

Location 3:
Where It Is: The corridor leading into the room with the flashing light, one corner tile can be clipped through.
Where It Takes You: This takes you into the basement in the dark corridor by the side room with the orb, grenade launcher, and doll head.

Location 4:
Where It Is: One tile in the section with the flashing light next to an acid hole, near the red corridor.
Where It Takes You: Into the basement section. There isn't much point to this one seeing as the acid hole is right next to this.

Location 5:
Where It Is: The red corridor connecting the pulse rifle room with the shelves with the small room with the flashing light. The entire floor is clippable here.
Where It Takes You: A corridor of the basement section leading to the fan. As with the previous location, there isn't too much point of using this one because of its proximity to the acid hole.

Location 6:
Where It Is: The room with the hamster wheel, pulse rifles, and destructible shelves, adjacent to the red corridor of the previous location. A tile right next to the red corridor, a narrow strip by the window on the side of the facehugger room, and one other tile on the other side of the room by the computers, can be clipped through.
Where It Takes You: As with the previous two locations, these all take you onto the strip in the basement leading to the fan that shoots you up.

Location 7:
Where It Is: In the corridor nearby the fan, next to the first side-passage. Looking straight down at the grated floor, you can clip through.
Where It Takes You: This takes you into the basement section by the skeeter launcher.

Location 1:
Where It Is: The wall here is the floor inside the truck itself. Quite a bit of the floor (though not the whole thing entirely) can be clipped through and you'll see the map in a weird way (untextured sections, broken walls, etc.).
Where It Takes You: This takes you under the truck itself, which isn't supposed to be an area that aliens can get to. You can use this to hide from enemies, but more importantly, you can actually push yourself into a completely new and previously inaccessible area (see the video).
https://www.youtube.com/watch?v=PhnyHaY6nV4

Location 1:
Where It Is: This is a very small section in the corridor leading up to the orb, after going up the first set of stairs, right after passing the minigun side passage. Hang out on the ceiling and look at where the floor turns slightly blue.
Where It Takes You: This drops you right into the blue tractor room, by the unbreakable light near the middle side passage leading away. It's a fun little shortcut, though it takes practice pulling it off right.

Location 1:
Where It Is: This is the small vent corridor that pushes you outside. Climbing on the wall further away from the main outdoor section and looking out, if you leap directly at the wall, you'll clip through it.
Where It Takes You: This sends you right outside into the main outdoor section. The best way to perform this jump in my opinion is actually to turn yourself completely upside down, as you'll gain more distance that way. See the below picture for that:

Location 2:
Where It Is: This is in the subway area on the ceiling of tracks section right above the connecting bridge part of the train.
Where It Takes You: This actually takes you directly beneath the train more often than not. I'm not sure what the function is, I guess a surprise attack against a camper can work here.

Location 3:
Where It Is: This is the same spot as the previous one, except this time it's inside the train itself. This works in the section with the SADAR as well as in the dark area and the other side with the pulse rifles, but only near the middle bridge.
Where It Takes You: Again, this takes you below the train. This I can see a bit more use for, especially if someone knows you're inside the train and is preventing you from leaving.

There are no known clippable walls in Elevator.

There are no known clippable walls in Lab 14.

Location 1:


Where It Is: This is the entire hive floor in the main arena area (with the predator orb, minigun, etc.). Climb onto the ceiling, look down, and simply jump at your leisure. Not the entire floor is clippable, but the majority of it is.
Where It Takes You: Right into the central arena section. This is great for a surprise attack and for getting right in the meat of things when people don't know where you are (hiding on the ceiling in the above area makes you very difficult to spot because it's so dark).

Office is the most exploitable map in regard to wall-clipping. Almost every floor in the main and upper areas of this map can be clipped through.

Location 1:
Where It Is: In the basement area next to the pulse rifles.
Where It Takes You: This simply takes you right below, onto the bottom floor of the furnace section. Not much point to this one seeing as it's right next to a hole anyway.

Location 2:
Where It Is: The main office floor. You can clip through a lot of this first extremely open section, though unfortunately not along the entire floor.
Where It Takes You: This will take you into the below floor in the section between the the predator orb and the pulse rifles by the wall. This is great for escape and simple practice, though doesn't really have any other uses given how exposed you'll be on the ceiling.

Location 3:
Where It Is: The three enclosed sections between each of the tables. For the two areas on the left, you can't clip through the upper opening section, but for the third one on the right (by the sink), you can.
Where It Takes You: The basement section with the barred floor, by the medkit and right above the stream of fire.

Location 4:
Where It Is: A large portion of the main office area by the soda machine. Note the strip by the far wall can be entirely clipped through.
Where It Takes You: Again, to the basement section, this time by the flamethrower and spiral staircase. Note that it's actually possible (though very difficult) to actually get yourself to fall out of the map by jumping at a space that takes you between the spiral staircase and a wall.

Location 5:
Where It Is: In the bathroom with the smartgun. Only a small corner can be clipped through.
Where It Takes You: This takes you to the basement section by the flamethrower.

Location 6:
Where It Is: The top floor bathroom with the pistol. Only a small area of this floor can be clipped through.
Where It Takes You: This takes you into the bathroom on the floor below.

Location 7:
Where It Is: On the top floor, this is the area with the computers between the bathroom and the staircase. Most of the floor here can be clipped here, though note that the floor in the minigun room can't.
Where It Takes You: This takes you into the main office floor, the area near the soda machine.

Location 8:
Where It Is: On the top floor, this is the second sections with a lot of computers.
Where It Takes You: This will take you again onto the main office floor, by the computer desks and tables.

Location 9:
Where It Is: On the top floor, this is the small room with the skeeter launcher.
Where It Takes You: This will again take you onto the main office floor, in an open space.

Location 10:
Where It Is: On the top floor, this is the area next to the previous one, with the table holding the AvP Gold box, holding an armor pickup. Most of the floor here can be clipped through.
Where It Takes You: This takes you into the main office floor in either the room with the medkit and coffee or the darker one with the armor and pistol.

Location 11:
Where It Is: On the top floor, this is the area with the wired ceiling revealing a starlit sky. The entire floor with the medkit can be clipped through.
Where It Takes You: This takes you right into the office section below. This can be a great surprise attack.

This guide was written solely by me (Olde). Credit goes to BROOD-SkorpioN for showing me the existence of wall-clipping and some clippable locations in Statue; credit to BROOD-Interloper for showing me some locations in Office. All other locations were discovered by me. You can (and should!) use this guide and share it with others. However, you should not distribute it while giving authorial credit to either yourself, someone else, or to nobody at all. You may quote from it at length but please do not post the entirety as a guide on any other forum or site without my express permission. I also reserve the right to remove or modify this guide at any time and/or make it unavailable, with or without providing a reason.

I hope you enjoyed this guide! I value your input so please leave a comment below! Thanks for reading!