The silver cap? At the very back of the marker? If it's your ram cap, it's meant to be removed by hand, but it's in there really tight. So take something with rubber grips, or a pair of pliars )sp?) with cloth around the cap (so you don't scratch the crap outta it) and twist it off. Bob's shop seems to put em in tight as hell, probably so they don't vibrate loose when you use it.
A Haiku about Life - By Secret Asian Man
twitch slaps me around
he likes to make me his *****
Because of small cock