Butterfly Knife - Wikipedia

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.

A version known as faux-channel construction also exists, where the handles are sandwiched between channel spacers that mimic the feel of a channel handle while being customizable with different types of spacers. Another variation is speed-channel construction, where a hole is milled out on the outside groove of the handle to support flow while flipping.

Sometimes, the handles can be made smaller in width to support a scales/liners system. Scales are the main handle construction in either the sandwich construction or the channel construction. Liners are the outside cover to make the full-sized handle. These liners are commonly made from G10 fiberglass or carbon fiber.

Additionally, the two main construction types can be combined to form a "chanwich construction", a portmanteau of "channel" and "sandwich", which involves two halves of a channel handle screwed together. The chanwich construction can be divided into 2 types: standard chanwich and speed chanwich. 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 to some extent, as well as easier access to the inside of the handle for cleaning.

There are also three types of pivots systems that balisongs use: bearings, bushings, or washers-only.[12]

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.

There are 2 types of pin systems: tang pins, small pins on the tang of the blade that space the handles, preventing them from hitting too hard, stopping blade wobble, and engaging the latch; and zen pins, which are two small pins embedded in the top of the handles of the balisong that make contact with the bottom of the blade. In certain knives the zen pins are hidden, embedded into the handle construction. While a balisong with zen pins is easier for the 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 to be 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 the pinless is exceedingly short and not meant for long-term usage before the system itself fails and the knife breaks.