Martial arts history is always a mix of fact and fable. For example, many students are taught that Okinawan kobudo developed when the Japanese, specifically the Satsuma clan who occupied Okinawa in the early seventeenth century, took away the Okinawan's weapons. On its face, the historical record doesn't support this. While weapon ownership was heavily regulated by the Satsuma, documents giving Okinawan samurai permission to transport their swords to southern Japanese master smiths for repair and maintenance clearly indicate the weapons were still in the Okinawan's possession. Another "tradition" holds that the sai were used as a preferred weapon by Okinawan police forces. This sounds plausible but isn't supported by the available documents. If the weapon was used this way there should be laws or regulations describing its use. Since no such documentation exists, this possibility has to be viewed with suspicion.

Speaking specifically about the sai, conventional wisdom often sites its origin as a farming implement. In reality, historical documents show that it originated as a longer weapon in mainland China and almost certainly came to Okinawa along the Fuchien trade route along with the white crane practioners whose training combined with the local Okinawan self-defense systems to form modern day karate.

The tight restrictions imposed by the Satsuma led to the development of kakushi buki, the use of concealed weapons, in which the sai had a prominent role. To be useful in kakushi buki some modifications had to be made to the traditional sai form. First, the weapon was shortened so it could be hidden in an obi or kimono sleeve. Second, the "side prongs" or yoko were straightened to avoid catching in concealing fabric when the weapon was drawn. The small size allowed a practitioner to have as many as three weapons concealed on his person. The third weapon was often used for throwing with the remaining two held in reserve for hand-to-hand defense.

When held against the arm, the metal shaft should extend 1" past the elbow and the handle should extend 1" past the tip of the index finger. This guarantees that the entire arm is protected during blocking movements and lets the weapon's metal ends increase the effectiveness of striking techniques. Traditional versions of the weapon were made of steel and had to be maintained with some kind of plant oil to prevent rusting.¹ Modern version are chrome plated.

The traditional methods of sai-jutsu are a little unclear. The yoko are clearly useful in trapping weapons and for restraining techniques worked against joints. I've heard it suggested that the use of the sai to trap strikes by bo is impractical. This theory suggests that the sai won't be able to stop the momentum of a full-force bo strike. While this idea is credible the method is inconsistent with the white crane origins of traditional Okinawan karate. An attempt to use a sai to forcibly intercept an incoming attack, e.g. with a forward thrusting motion, could easily cause arm or wrist damage. A more appropriate defensive method would be to use the weapon's long shaft to redirect the incoming attack with a sideways motion. The interception would take place after the attack has reached its full extension where its momentum is minimal.

The sai also have practical use in "body conditioning". A standard sai weighs in the neighborhood of 1.5 pounds or .7 kg. The common flipping techniques, worked repetitively, condition both forearms and the hands and wrists.

sai parts

¹ If you have one of these sai you should avoid getting the oil on the handle to prevent slipping.