Butterfly knives, also known as Batangas knives or balisongs, are folding pocket knives that originated in the Philippines. Because of the dangerous qualities of the knives, they have been banned in many Western nations, including parts of the United States, the United Kingdom, Canada, Australia and Germany.
When butterfly knives are closed, their blades are completely concealed. They have two handles that counter-rotate around the tang that, when closed, cause the blades to be hidden in the handle grooves. Because of these factors, butterfly knives can practically be as strong as fixed blade knives.
Because of the unique and interesting design of butterfly knives, they can be opened or closed very rapidly using just one hand. This can be done with a flair that is both exciting and fascinating to watch. However, because the opening and closing of the butterfly knife is so unusual, it was portrayed a lot in films and TV programs in the 1970s and 1980s, often being depicted as very dangerous. They were usually carried by villains and criminals.
Not only is it illegal to carry any knife with a blade over 7.63 cm (3 inches) in the UK, it's illegal to own a butterfly knife at all. They are on a list of banned weapons that includes switchblades and a number of martial arts weapons.
Butterfly knives were first mentioned back in 1710 in a French book called "Le Perret," which described them as being used in the 1500s as a utility knife. Referred to as "Balisong" in the Philippines, the word is thought to have come from the Tagalog words "baling sungay" (broken horn). The original balisongs were made out of carved animal horns.
Butterfly knives are also illegal in some parts of the United States. It is illegal to send butterfly knives through the U.S. Postal Service. Spyderco, a knife manufacturer, pleaded guilty in a U.S. Federal court case for sending butterfly knives in the mail between June 2005 and January 2007, and the company was fined £48,750.