Step 1: Materials and assembly
Take a BB and place it in the "jaws" of the mauly. Then try to keep the BB held in the jaws without flying out (this does take some practice and some luck). Use the tip of the pen to force the BB far enough forward to be pushed out of the mauly.
It is not my fault if one of these things shoots you in the eye. Use at your own risk just like everything else on this site.