The sai is a three-pronged truncheon sometimes mistakenly believed to be a variation on a tool used to create furrows in the ground.
This is highly unlikely as metal on Okinawa was in short supply at this time and a stick would have served this purpose more satisfactorily for a poor commoner, or Heimin.
The sai appears similar to a short sword, but is not bladed and the end is traditionally blunt. The weapon is metal and of the truncheon class with its length dependent upon the forearm of the user. The two shorter prongs on either side of the main shaft are used for trapping (and sometimes breaking) other weapons such as a sword or bo.
A form known as nunti sai, sometimes called manji sai (due to its appearance resembling the swastika kanji) has the two shorter prongs pointed in opposite directions.