Play polissa massa any leel any era and goto the CP the forcefield(the one after the two tunnels) theplace where snipers like to hang out ande wait for bady guys.idk its number sorry
anyways go to the CP light and you will see grey boxes in a corner of the island type thing jump the boxes and you should be in between the boxes and wall for a minute then you will end up going through the wall BUT be carefull once you are in if you move you may et stuck permantly but if you dont move much or at all you should b able to escape if you want and you should also be able to shoot enemies.