Balisong

A Balisong, otherwise known as a butterfly knife or fan knife, is a folding pocket knife with two handles counter-rotating around the tang such that, when closed, the blade is concealed within grooves in the handles. It is sometimes called a Batangas knife. In the hands of a trained user, the knife blade can be brought to bear quickly using one hand. Manipulations, called "flipping" or "fanning", are performed for art or amusement.