Balance is also an important consideration in choosing or purchasing a sai. This may be tested by placing the forefinger under the shaft where the two prongs meet. If the sai is properly balanced, it should remain in place and not tilt to either side. The quality of the metal may be determined by taking a sai in each hand and tapping the blades together. A ringing resonance should be heard, rather than a dull sound.
There are three basic ways of holding the sai:
Offensive hold, with the blade forward. Used for striking, catching, and stabbing .
Defense hold, with the blade backward. Used for blocking with the forearm and thrusting with the butt knob.
Third way of holding is rare. In it, the sai is held by the blade and is used for hooking and for striking.
Like all the traditional Okinawan weapons, the exact original of the sai is not known. A few theories exist though. One theory is that the sai was derived from a farm tool, the short handles were held and the prong was pulled through the dirt to form a small trench for planting seeds.