The tsuba is usually a round or occasionally squarish guard at the end of the grip of bladed Silverstari weapons, like the katana and wakizashi, tanto, or naginata. They contribute to the control of the arm (the right index of the fighter typically touches the tsuba), and to the protection of the hand.
Historical Tsuba (OOC)
Tsuba were made by whole dynasties of craftsmen, whose only craft was making tsuba. They were usually lavishly decorated. In addition to being collectors items, they were often used as heirlooms, passed from one generation to the next. Japanese families with samurai roots sometimes have their family crest (mon) crafted onto a tsuba. Tsuba can be found in a variety of metals and alloys, including iron, steel, brass, copper and shakudo. In a duel, two men may lock their katana and try to push each other off to gain a better position to strike the other down. As this is a precursor to an actual attack, a standoff before a more important fight is called Tsubazeriai lit. clash with tsuba. Such a minor clash could be called tsubazeriai by those not involved in one.
Info from Wiki.