First off this is a very hard glitch and takes lots of practice and must be online to do it.Now you go to a place were you can JUMP over cover not climb up. Now go to cover and aim your camera down so its above your head. Then hold up and you see the sighn to jump over then (very quickly) press down and A so you start to float (levitation glitch). Then press down and A and B and you will flip up in the air. You can get out of almost every map with this and is harder to do with the chainsaw.