Tsuba are the swordguards on Samurai swords. They are small round slabs of metal, about four ounces at most. In the center is a long traingular slot that fits around the blade. The tusba themselves were ornate and beautiful and quite creative and forged from bronze or pewter or brass or steel. Just like the US hunter of days past engraved hunting scene on his shotgun, so too did the Samurai so adorned their own weapons.
Sources: wiki, http://www.arco-iris.com/George