you dont get stuck in the wall, you get to the other side.
you see, well if you map, you make a sort of environment and then wrap it up with a skybox. like this :
so when you are in the offlimits area, you can still move around and stuff.
also you can see what happens in the normal are because mappers use nulling, a tool that makes it algg less, which prevents some surfaces from being drawn.
nulled surfaces get "invisible", so you can see through the brush.
all is, you'll get a place where you cant be seen, can see your enemy and can damage your enemy if you are in the offlimits area.