Before I start I just want to say it really does work, I do it with my friends and we can get to really high rounds, even search on YouTube.
First of all you can do it on most maps, the ones I have done it on are... Five, kino der totten and verruck, as well as different maps there is multiple barriers to get out.
Let's start with five, the room you start in has four barriers two at each end where there is a teleporter when the power is activated, and two at the opposite end. In my opinion the two at the other end are best and i'll tell you why (you can get out all four!!!)
To get out you must knife the bottom right of the glass then build that one barrier, you can then knife the rest of the glass but don't build any barriers, (this will be the same for any barrier, make sure it is that block of wood that you use). Crouch on the far left end of the block and wait for a zombie, (note the host can't get out) when the zombie is about to take it away press start then triangle afterwards in a fast motion, you should be pulled in with the barrier, ASAP exit the start menu and kill the zombie before it kills you!!!
Now that you are out the map you can wonder about or get ontop of the roof of the elevator room, but be careful zombies can still get you!!! If you got out of the left barrier, to the right there should be long verticle windows, you can walk through them, do so. This will take you to the room where the right barrier is. If you keep running up the right side of this room, you will find a filing cabinet with different world times on the wall above. At the left of the cabinet you should be able to jump on top of it, once ontop you can get on the clock at the right hand side then diagonally to your right jump on the black line and walk through the wall. Now you must run down to the light just before the elevator, crouch down just a tiny centimetre before the small circle within the big circle and DO NOT MOVE!!!
Now comes the boring but main part of this whole thing, leave your guy sitting there whilst the other members of the party/lobby camp in the elevator, zombies should gather below you and not get the other players, if it is your turn for the pentagon thief, (the guy who takes your guns) he will also stand there, bad news for you is you need to stay there for a while, and that's five.
If I get enough thanks or rep I'll post which barriers and what to do once out of kino der totten and verruck, also if you want to find out other barriers that you can do kool stuff with and get of, message me or visit my profile page, thank you for showing interest. xXsCrEaMeRXx.