Before its arrival in Okinawa, the sai was already being used in other Asian countries including India, Thailand, China, Vietnam, Malaysia, and Indonesia. It may have been brought to Okinawa from one or several of these places simultaneously. Silat practitioners typically refer to the sai either as chabang in Indonesian or tekpi in Malay. Based on the Indian trisula, early evidence in the form of Japanese art shows that the chabang predates the sai’s use in Okinawa and China The word trisula itself can refer to either a long or short-handled trident. Because the trisula was created in South Asia, it is possible that the sai originated in India and spread along with Hinduism and Buddhism. This is supported by the fact that the trisula is important as a Hindu-Buddhist symbol.
In Okinawa the sai was used by domestic police (ufuchiku) to arrest criminals and for crowd control. Use of the sai in Japanese martial arts was improved in 1668 by Moto Chohei, an Okinawan prince.
The sai eventually reached Japan in the form of the jitte, which usually has only a single prong although some jitte have two prongs like a sai. Both are like truncheon weapons, used for striking, bludgeoning, and also for multiple punctures over different positions on the body.
The sai is typically used in pairs, with one in each hand. Five kata are commonly 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 utility of the sai as a weapon is reflected in its distinctive shape. It is primarily used as a striking weapon for short jabs into the solar plexus but it also has many defensive techniques.
There are several different ways of wielding the sai, which give it the versatility to be used both lethally and non-lethally. 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. 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 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.
Because there is no morphological plural in Japanese, the word “sai” refers to either a single weapon or multiple. Nicho sai refers to a kata that uses two sai, while sancho sai kata refers to kata using three sai.