Any standard size doors, both single and double. After running in and closing the door behind you, the door appears to "catch" you and reopening and shutting does nothing. If the zombie is on one side of the door and you on the other (even what appears to be outside of their hit box) they can still strike you. It's basically a death sentence because there is no reasonable way to release yourself. Also you cannot fire at/attack the zombie, because it appears that the game thinks you are on one side of the door and the zombie on the other, but for some reason, you can still be attacked.