Sai are martial arts weapons
that are similar in size, shape, and construction to a knife
with a large two-pronged forward-pointing handguard, but differ from a blade
in that there are no sharp edges. This is because the weapon was developed as a karate
"non-weapon", that is, a device that is lethal
in the hands of an expert without appearing as such to the casual eye. It joins many other karate weapons such as the Bo
, and Tonfa
in that regard, as they were initially wielded by peasant
s who were not allowed bladed weapons by their feudal
lords in ancient China
, and Japan
The tip of a Sai may be narrower than at the handle, but will not be pointed. It is, however, quite dangerous in a jabbing attack, and can also be thrown. Another useful function of Sai are to block swords and other blades, as it is one of the few metal karate weapons. In this it was similar to the jitte, as drunken warlords/samurai/bandits armed with swords were actually a regular danger. There was even a practice called a "crossroads cut" in which a Samurai would take a newly-made Katana to a crossroads and try and cleave the first person he saw in half to blood the blade.
An artist wields a Sai either in a "standard" knife grip, or in a Tonfa-style grip with the long portion of the weapon extending under the forearm for a reverse jabbing attack with the portion protruding beyond the elbow. Often three are carried, so one can be thrown prior to closing with the enemy. Due to their non-bladed nature, they are best suited to a sudden surprise attack, as they are usually carried in the sleeves of an Obi, or in a defensive posture against a blade-equipped foe as previously mentioned.
-TheChronicler pointed out that often the user's thumb will wrap around the yoke (the center cross part), so that the sai can be flipped in and out from one position to the other, pivoting on the thumb.