You need two players for this cheat. Go to the wall in the back of the hangar.

Go into forge mode and make sure you're facing the wall. Create a spawn point while touching the wall .Make sure that all other spawn points on the map are deleted.

Kill yourself and you'll be behind the wall. You have to be touching the the front or back wall or it will say return to the battlefield.

To get out touch the front wall and create a spawn point there. Delete all the spawn points in the wall.