# Butterfly knife

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"). An exceptionally large balisong is called a balisword.
The balisong was commonly used by Filipinos, especially those in the Tagalog region, as self-defense and a pocket utility knife. Hollow-grind balisongs were also used as straight razors before conventional razors were made available in the Philippines. In the hands of a trained user, the knife blade can be brought out to bear quickly using one hand. Manipulations, called "flipping", are performed for art or amusement. Blunt "trainer" versions of these knives are also 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.

## Name

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.
The name "balisong" is derived from barangay (village) Balisong, part of the municipality of Taal, Batangas province, which along with the neighboring barangay Pandayan (now part of Poblacion zones 6, 9, and 10 of Taal town proper), 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 was 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 29 cm (11 in) long when opened.

## History

The origin of the knives is unclear. Oral histories claim that the knives were first created in the Philippines in 800 CE. However, there is no documentation or archeological evidence to back this. Balisong's mass production in the Philippines can only be attested to the early 1900s. Another claim is that balisong was originally an adaptation of a French measuring tool called the pied du roi ("foot of the king"), invented between the 1500s to the late 1760s. However, how it was introduced to the Philippines is unknown. There are theories that it may have been introduced by sailors in the Spanish Empire, which was then allied with France.
Regardless of origin, the modern balisong was perfected in the Philippines, where it became much larger, and was predominantly used as a weapon, not just a tool. The quick opening techniques ("flipping") were also developed in the Philippines. In contrast, the French pied du roi was primarily a folding ruler, with the knife only included in some specimens as a novelty. They were cumbersome to open and unlikely to be used for self-defense, especially since they also commonly included a metal tang at a right angle from the end of the handle to aid in measuring. There were also very similar designs to the balisong produced in England in the late 19th century, presumably also derived from the pied du roi. But like the latter, they were primarily utilitarian tools.

## Construction

There are two main types of balisong construction: "sandwich construction" and "channel construction".
Sandwich-constructed balisong knives are assembled in layers that are generally pinned or screwed together. They allow the pivot pins to be adjusted more tightly without binding. When the knife is closed, the blade rests between the layers.
For a channel-constructed balisong, the main part of each handle is formed from one piece of material. In this handle, a groove is created (either by folding, milling, or being integrally cast) in which the blade rests when the knife is closed. This style is regarded as being stronger than sandwich construction.
Additionally, the two constructions can be combined to form the "chanwich construction", which involves two halves of a channel handle screwed together. Although rare, this construction generally keeps the best elements of both constructions and discards the worst, as it retains the better handle shape channel construction is known for, while still allowing adjustment of the tightness the handles are held together with to some extent, as well as easier access to the inside of the handle for cleaning.
There are also three methods of operation balisongs use: bearings, bushings, or only washers.
Bearing-operated balisongs have small ball bearings housed in a circular concavity around the hole in the pivot. These bearings allow the handles of the balisong to rotate.
Bushing-operated balisongs have a small metal bushing slightly thicker than the tang in each pivot hole with a usually bronze disc known as a washer on each side. These washers clamp down on the bushing, but not on the tang, when the pivot screw is tightened, allowing the handle to rotate around the tang.
There are also washer-only operated balisongs which are usually much cheaper and lower quality than the other kinds, as they don't need bushings, but the handles will always bind to the tang when the screws are tightened enough and the washers, tang and handles all wear themselves down much faster due to the increased friction.
Some of the blades of traditional butterfly knives in the Philippines were made from steel taken from railroad tracks, thus giving them a decent amount of durability and toughness, while others are made from recycled leaf springs of vehicles.
Most modern balisongs do not use tang pins. Instead, they use "zen pins", which are two small pins embedded in the top of the handles of the balisong which make contact with the bottom of the blade. While a balisong with zen pins is easier for end user to perform maintenance on for the end user and significantly easier to design; they do not hold up as long as tang pins would in a properly made knife. the force of the harder blade contacting the soft zen pins will mean they need replaced far more often than tang pins which should be mild steel so the blade doesn't crack and can cushion against soft handle materials rather than crush each other.
Some modern balisongs also have a "pinless" system, in which they do not have any pins, and instead rely on the material of the handles to make contact with the blade, similar to how zen pins work. The longevity of pinless is exceedingly short and not meant for long term usage before the system itself fails and the knife breaks.

## Parts
### Bite handle

    The handle that closes on the sharp edge of the blade, and will cut the user if they are holding that handle when the knife closes. This handle usually carries the latch.

### Choil

    The unsharpened portion of the blade just above the kicker, that makes it easier to sharpen the blade.

### Kicker (or Kick)

    Area on the blade that prevents the sharp edge from touching the inside of the handle and suffering damage. This is sometimes supplanted by an additional tang pin above the pivots.

### Latch

    The standard locking system, which holds the knife closed. Magnets are occasionally used instead.

### Latch, Batangas

    A latch that is attached to the bite handle.

### Latch, Manila

    A latch that is attached to the safe handle.

### Latch, Spring

    A latch that utilizes a spring to propel the latch open when the handles are squeezed.

### Latch gate

    A block inside the channel of the handles stopping the latch from impacting the blade.

### Pivot joint

    A pin about which the Tang/Blade/Handle assemblies pivot.

### Safe handle

    The handle (generally the handle without the latch) that closes on the non-sharpened edge of the blade.

### Swedge

    Unsharpened spine of the blade. Some balisongs are also sharpened here or on both sides with either a more traditional look or wavy edges similar to a Kris sword.

### Tang

    The base of the blade where the handles are attached with pivot pins.

### Tang Pin(s)

    Pin meant to hold the blade away from the handle when closed to prevent dulling; and, in some cases, a second pin to keep the handles from excessively banging together while the butterfly knife is being manipulated.

### Zen Pins

    Screws mounted inside the handles that collide with the kicker mounted on the tang to prevent the blade from moving around while in the open or closed position.

### Blade

    The blade is a piece of steel that runs down the center of the knife that is secured by both handles when closed. One edge of the blade is sharp and will cut the user if they are not careful, especially when flipping the knife. The other side is called the spine and can have what is known as a swedge. The swedge is a blunt bevel ground in for looks and won't cut the user. The spine commonly impacts the user's hand when flipping.

### Exploded bushing construction in a modern balisongBushing

    A small barrel of steel included in the blade so the handles can be tightened without back and forth movement. the bushing is a highly precise element of modern balisong knives and require specialized tuning to function properly.

### Replacement Parts

    for a comprehensive list on parts and other issues check out the balisong wiki dedicated to parts sizes and information on active balisongs in use here: https://docs.google.com/spreadsheets/u/2/d/1cYnDv67BTD9H8wd7D-R_URGXYq3AGT3MotrVE4OX6Js/htmlview

## Legal status

The balisong has been outlawed in several countries, mainly due to its easy utility in crimes and its ability to be easily concealed for the same purpose. In some jurisdictions, its criminal use is considered a knife crime.
* In Australia, balisongs are generally classified as a prohibited weapon, which requires a special, legitimate excuse to possess it. Australia defines balisongs as a flick knife (or other similar device) that has a blade which opens automatically by gravity or centrifugal acceleration or by any pressure applied to a button, spring or device in or attached to the handle of the knife.
* In Belgium, butterfly knives are illegal.
* In Canada, although not specified by name as a prohibited weapon, the balisong knife is often considered by courts to fall under the gravity knife or centrifugal classification and is therefore prohibited, unless grandfathered in before prohibition.
* In the Czech Republic, balisongs, switchblades, and gravity knives are treated like normal knives.
* In Denmark, butterfly knives are illegal.
* In Finland, balisongs are legal to be purchased, sold and possessed, and are treated just like regular knives and befall under the edged weapons law. Carrying one in public is permitted if the person carrying one can prove it is used as a tool.
* In France, balisongs are legal to own if one is over 18 years of age but are illegal to carry without official authorization.
* In Germany, the balisong was outlawed when the Waffengesetz (weapons law) was tightened in April 2003 in the aftermath of the Erfurt massacre. Thus, buying, possessing, lending, using, carrying, crafting, altering and trading it is illegal and is punishable by up to five years imprisonment, confiscation of the knife and a fine of up to €10,000. Using a butterfly knife for a crime of any kind – as is any illegal weapon – is punishable by from 1 to 10 years imprisonment.
* In Hungary, balisongs, switchblades and gravity knives are treated like normal knives. They are legal to possess one regardless of its length, but it is illegal to carry one that is longer than 8 cm (3.1 in) in public.
* In Ireland, butterfly knives are illegal offensive weapons.
* In Italy, balisongs are legal to own if not sharpened on both sides, but illegal to carry without justifiable reason.
* In Lithuania, balisongs among other knives are legal to possess and carry as they are not considered weapons. This excludes switchblades.
* In the Netherlands, balisongs are illegal.
* In New Zealand, balisongs are illegal.
* In Norway, balisongs are illegal.
* In the Philippines, it is now generally illegal to carry one without identification or a proper permit in the streets of the capital because of their prevalent use in crime and altercations. One now needs to demonstrate the need for professional livelihood or utilitarian purpose (such as cutting grass, preparing fruit and meat, being a vendor of knives, being martial arts instructors, etc.) to be able to walk around with bladed implements in the urban areas. Another rule of thumb is that the blade of pocketknives must not exceed the length of the palm and must not be openable by one hand to be considered as a utility knife, as opposed to a weapon (thus, Swiss Army Knives, are legal).
* In Poland, balisongs, switchblades and gravity knives are treated like normal knives.
* In Russia, balisongs are legal only if the length of the blade is not more than 90 mm (3.5 in).
* In Sweden, it's illegal to carry, import or trade a balisong, but legal to own and collect.
* In Switzerland, balisongs are illegal to carry, give, lend, buy, or trade.
* In the United Kingdom, the balisong has been legally classified as an offensive weapon since January 1989. Carrying one in public is an offence under the Prevention of Crime Act 1953. Sale, lending, hiring, giving or importing is prohibited by the Criminal Justice Act 1988, as amended by the Offensive Weapons Act 1996. Any imported are liable to be seized and prosecution may follow. An exception is made for knives of this type over 100 years old, which are classed as antiques.
* In some parts of the United States, it is illegal to possess or carry such a knife in public. In certain jurisdictions, balisongs are categorized as gravity knives, switchblades, or daggers.
** In California, balisong/switchblade knives are legal to own, buy, sell, and transport if the length of the blade is not more than 2 inches (51 mm). If the length of the blade is more than 2 inches (51 mm) they are illegal to buy, sell, transfer, or possess in public although it is legal to possess one if kept at home (Penal Code section 17235 & 21510).
** In Florida, butterfly knives are legal, as Florida defines butterfly knives as a type of folding knife. However, butterfly knives are subject to the same concealed carry licensing requirements as all other folding knives with blades longer than four inches.
** In Hawaii, it was illegal to possess, manufacture, sell, transfer, or transport any balisong/butterfly-type knife until the 9th Circuit Court of Appeals overturned the ban in August 2023.
** In Kansas, there were once legal restrictions on butterfly knives; however, as of July 2013, the Kansas Comprehensive Knife Rights Act decriminalized the carrying of all types of bladed weapons.
** In Illinois, it is legal to own and carry a butterfly knife.
*** In Chicago, it is illegal to carry a concealed knife with a blade longer than 2.5 inches (64 mm). Automatic (switchblade) knives and gravity knives are prohibited, as carrying a concealed double-edged knife.
** In Indiana, it is legal to own and carry a butterfly knife both concealed and open.
** In Kentucky, the balisong is legal for concealed and open carrying anywhere one is not otherwise prohibited from carrying a concealed deadly weapon. Kentucky's constitution and revised statutes prohibit cities and counties from enacting weapons laws and restrictions.
** In Maine, it is legal to own, sell, and carry.
** In Massachusetts, the balisong is legal for concealed and open carrying so long as it does not "[present] an objective threat of danger to a person of reasonable and average sensibility." Restrictions also apply depending on the area of the person carrying the knife (such as within a public school).
** In Michigan, the balisong is legal because it is classified as a folding knife.
** In New Jersey, balisongs are illegal (NJSA 2C:39-1), but the question of legality or illegality is open.
** In New Mexico, possession of a butterfly knife is illegal, because the butterfly knife is a switchblade within the meaning of the statute making possession of switchblades unlawful.
** In New York, the balisong has been determined not to be a gravity knife, and therefore not prohibited under the Penal Law [see: People v. Zuniga, 303 A.D.2d 773 (2nd Dept. 2003)] However, the law prohibiting gravity knives was found to be unconstitutional and their possession was decriminalized in 2019.
** In North Carolina, citizens are allowed to carry most pocketknives most of the time. Statute S.14-269, which prohibits the concealed carrying of any "bowie knife, dirk, dagger", or "other deadly weapon of like kind" doesn't apply to an "ordinary pocketknife carried in a closed position".
** In North Dakota, it is legal to own a balisong and carry it openly. However, they are illegal to carry concealed, as they are considered to be deadly weapons.
** In Ohio, it is legal to own a balisong and carry it openly, and illegal to carry concealed, as it is considered a deadly weapon.
** In Oklahoma, the balisong is legal for open carry but is illegal to carry concealed.
** In Oregon, it is illegal to carry a concealed balisong.
** In Tennessee, there are no restrictions in carrying a balisong and similar knives, whether open or concealed carrying. Restrictions on these instead focuses on intent rather than merely carrying.
** In Texas, switchblades are legal as of 1 September 2013.
** In Utah, balisongs are legal to own and carry as long as you are not a "Restricted Person" as described in Utah State Code §76-10-503.
** In Virginia, the balisong is legal for concealed, and open, carrying according to state law.
** In Washington, the balisong is classified as a spring blade knife, and under state law, one cannot manufacture, sell, dispose of, or possess such knives.
Balisong trainers feature a special blunt and unsharpened "blade" and are legal in some areas where balisongs are not.