tsuba (guard)
The tsuba (鐔 or 鍔) is usually a round or occasionally squarish guard at the end of the grip of bladed Japanese weapons, like the "katana" and its various declinations ("tachi", "wakizashi" etc.), "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.
The most common shapes of tsuba are round (maru gata), rounded-square (kaku gata) and four lobed (mokko) with many variations within each basic design.