Ballisong

A butterfly knife, also known as a balisong, fan knife, or Batangas knife, is a type of folding knife that originated in the Philippines. Its distinctive features are two handles that rotate counter-clockwise around the tang so that when closed, the blade is concealed within the grooves in the handles. Sometimes a latch holds the handles together, usually mounted on the one facing the cutting edge.

The balisong was commonly used by Filipinos, especially those from the Tagalog region, as a pocket knife and for self-defense. Hollow-cut balisongs were also used as straight razors before conventional razors became available in the Philippines. In the hands of a skilled user, the knife blade can be moved quickly with one hand. The manipulations, called "flips," are done for artistic or entertainment purposes. Blunt training versions of these knives are available that can be used to practice tricks without risk of injury.