Sai is the Ryukyu name for a traditional Okinawan weapon.
The basic form of the weapon is that of a pointed, rod-shaped baton, with two long, unsharpened projections (called yoku) attached to the handle. The very end of the handle is called the knuckle. Contrary to popular belief, the shaft of a traditional sai is not a blade.
Sai are constructed in a variety of forms. Traditional sai are round, while some reproductions have adapted an octagonal middle prong. The yoku are traditionally symmetrical, however, the Manji design developed by Taira Shinken employs oppositely facing yoku in an approximation to the Manji symbol (also known as the Swastika) from which it takes its name.
Some believe that the sai was always intended as a weapon while others hypothesize that it originated as an agricultural tool used to measure stalks, plow fields, plant rice, or to hold cart wheels in place. Evidence for the latter theory is limited. The sai is known to have been used in other parts of Asia before its arrival on Okinawa, such as India, China, Indonesia, Siam and Malaysia. Early evidence suggests Indonesia or the neighbouring area as the sai’s point of origin. In Malay the sai is known as a “chabang” (also spelled cabang or tjabang, meaning branch) and is thought to derive from the Indian trishula. The chabang quickly spread through the rest of Indo-China and may have reached Okinawa from one or more of these places simultaneously. In Japan it might have been known as the San-Ku-Chu.
The sai’s utility as a weapon is reflected in its distinctive shape. With skill, it can be used against a long sword by trapping the sword’s blade in the sai’s handle. If the user is skillful enough she/he may be able to fracture a blade or other weapon with the sai. There are several different ways of wielding the sai in the hands, which give it the versatility to be used both lethally and non-lethally. The sai is primarily used as a striking weapon or for short jabs into the solar plexus. The sai also has many defensive uses in blocking other weapons.
One way to hold it is by gripping the handle with all of the fingers and pinching the thumb against the joint between the handle bar and the shaft of the sai. This allows one to manipulate the sai so that it can be pressed against the forearm and also help avoid getting the thumb caught in the handle when blocking an attack. The change is made by putting pressure on the thumbs and rotating the sai around until it is facing backwards and the index finger is aligned with the handle. The sai is generally easier to handle in this position. The knuckle end is good for concentrating the force of a punch, while the long shaft can be wielded to thrust at enemies, to serve as a protection for a blow to the forearm, or to stab as one would use a common dagger.In practice, some prefer to keep the index finger extended in alignment with the center shaft regardless of whether the knuckle end or the middle prong is exposed. The finger may be straight or slightly curled. Used in this way, the other fingers are kept on the main shaft, with the thumb supporting the handle.
The grips described above leverage the versatility of this implement as both an offensive and a defensive weapon. Both grips facilitate flipping between the point and the knuckle being exposed while the sai is held in strong grip positions.
The sai is typically used in pairs, with one in each hand. In the United States a common style is Yamanni Ryu. Five common kata are typically taught, including two kihon kata. The style includes a variety of blocks, parries, strikes, and captures against attackers from all directions and height levels. Use of the point, knuckle and central bar is emphasized, as well as rapid grip changes for multiple strikes and blocks.
The jitte is the one-pronged Japanese equivalent of the (Okinawan) sai, and was used predominantly by the Japanese police during the Edo period. It is a featured weapon in the curriculum of several Japanese Jujutsu and koryu schools.