butterfly knife

A balisong, also known as a butterfly knife, fan knife or Batangas knife, is a type of folding pocketknife that originated from the Philippines. Its distinct features are two handles counter-rotating around the tang such that, when closed, the blade is concealed within grooves in the handles. A latch sometimes holds the handles together, typically mounted on the one facing the cutting edge (the "bite handle"). An exceptionally large balisong is called a balisword.

Butterfly knives in closed and open positions