Mate 4 Life. Someone who you can tell stuff to and it will stay in the vault. You may not talk everyday; they wont hold it against you but you know they'll always be there. You can just pick up right where you left off. You can totally let loose with an M4L. You don't need to be politically correct with them at all and it's all good! You accept them exactly for who they are and they accept you. No judgements whatsoever. You're completely honest with one another calling them on their shit if need be.
Person 1:Mate, thanks for being there to post bail I didn't know who else to call...M4L
Person 1: I really need to talk to you, but it's gotta stay in the vault.
Person 2 Fuk yeh! whats up?