"This is a balisong, or butterfly knife," Harry explained. "It has one blunt edge and one sharp edge. The handle is split in two, and folds around the blade when it's stored. That means"—Harry flipped the knife shut again—"that you can open and close it with one hand. It also means you can do all sorts of tricks with it"—with a long series of click-clack-click-click-clack-click-clacks, Harry put the knife through a series of twirls, spins and even tosses that left Dean gaping—"which make you look like a street tough's worst nightmare."