Flameswor10 is correct; that is the cam position hack, which allows you to have a different view of the map/battle zone. This would be one of the options that allows you to be below the map and shoot upwards. The other option would be as if you were flying, without the fly hacks. This hack is particularly useful for anti-camping purposes or getting a different angle to take a shot. For cabin fever, it could be useful for seeing the entire map and all of the enemies, but isn't very good when the entire house is being swarmed. Also, the distance required to shoot actually makes it worse and will make aiming difficult, the end result being a lower score and remarks from your teammates about why you are shooting at the ceiling. Another thing to note is that this hack is client sided (to some extent), meaning that while you see yourself above or below the map, everybody else (and the server) sees you staring at the ceiling/shooting at the walls.