Allen or hex key to unlock the top, then you turn the pin down like you're trying to engage a pin valve. Turn it as far as you can go then you might need a pair of pliars to grab the pin from the under side and continue turning till it screws down and out.
It has it's advantages for paintball. You could lose your knob if you had it backed out too far and then you'd have no way to play. Mine can't be backed off unless I want to back it off. Not that i've ever played.