It's really easy, too. No modification required, and not too much stressing on the plastic. Virtually none, in fact. All you have to do is fold in the hands as if you're transforming the arm, then close the forearm up again and slip the other end of the morning star over the end of the arm. Like this: Also, the hands are a decent shape to take GI Joe weapons. The fingers are spaced out just right. The ideal if you're into giving robots swords is the Masamune from the old Extra Knights Final Fantasy Sephiroth, as it's got a peg that'll stop the sword from flopping about too much.