The balisong or butterfly knife is a form of folding pocket knife with two handles that counter-rotate around the tang such that, when closed, the blade is concealed within grooves in the handles. In the hands of a trained user, the knife blade can be brought forth quickly using one hand.
The butterfly knife originated in the Philippines in the province of Batangas where it is a very common everyday knife known as a balisong. After World War II many American soldiers brought these knives home as souvenirs, introducing them to the Western world.
In many U.S. states, it is illegal to possess and/or carry such a knife in public; indeed, doing so is a felony in some states, such as Nevada.
External links
Video footage of the techniques for using a butterfly knife (http://www.balisong.net/en/techniques.htm)
Legality checklist for various states in USA (http://www.thehighroad.org/library/blades/knifelaws.html)
Balisong is a tagalog (Filipino dialect) word, originated from the Batangas province (south of Manila, Philippines islands).
Balisong means "broken horn" and refers to the mobile handle which protect the blade when closed.
Several people are employed to prepare and insert the various inlays used to decorate a balisong and put together the blade, the handle and the latches.The blade of a balisong is made from several materials depending on the quality required by the manufacturers.
The balisong is one of the most brilliantly designed knives: It's handles act as the knife's sheath, and once open the balisong is one of the few folding knives almost as strong as a fixed blade.
The balisong has a rich history dating back at least to the 19th century, and is used in Filipino martial arts.
Because balisongs have been stigmatized by law enforcement and movies, and because the design is often confusing or too "fancy" for the typical sportsman, balisongs are made in much fewer quantities than other kinds of pocket knives.