A butterfly knife, also known as a balisong, fan knife or Batangas knife, is a type of folding pocketknife that originated in 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"). The balisong was commonly used by Filipinos, especially those in the Tagalog region, as a self-defense and pocket utility knife. Hollow-grind balisongs were also used as straight razors before conventional razors were available in the Philippines. In the hands of a trained user, the knife blade can be brought to bear quickly using one hand. Manipulations, called "flipping", are performed for art or amusement. Blunt "trainer" versions of these knives are available and can be used to practice tricks without the risk of injury. The knife is now illegal or restricted in some countries, often under the same laws and for the same reasons that switchblades or concealed weapons are restricted. Within the Philippines, it is no longer as common in urban areas as in the past. Etymology The name "balisong" is derived from barangay (village) Balisong, part of the municipality of Taal, Batangas province, which along with the neighboring barangay Pandayan, were the original manufacturing centers of the knives in the Philippines. The two barangays were home to a blacksmith industry that also produced other bladed implements such as bolo knives. It is also claimed that the meaning of the term balisong is derived from the Tagalog words baling sungay (literally, "broken/folding horn") as the hilt of the blade were traditionally made from carved carabao and deer horn, as well as bones. The traditional balisong is also known as veinte y nueve, or "twenty-nine," in the Philippines, because they are long when opened. Other names for the knives in English include "fan knives" and "butterfly knives" from the motion, and "click clacks" from the sound they make when they are opened and closed. History The origin of the knives is unclear. Oral histories claim that the knives were first created in the Philippines in 800 AD. However, there is no documentation or archeological evidence to back this. Balisong mass production in the Philippines can only be attested to the early 1900s. Another claim is that balisong were originally an adaptation of a French