A buckler is a small shield, 15 to 45 cm (6 in to 18 in) in diameter, gripped in the fist; it was generally used as a companion weapon in hand-to-hand combat, as its size made it poor protection against missile weapons (e.g., arrows) but useful in deflecting the blow of an opponent's sword or mace. There are two major forms of medievally documented bucklers. The first is a simple round shield with the fist positioned directly behind the boss with a variety of shapes of face and depths of rim. These could also have projections from the top and bottom or serrated rings around the boss. The second major form is a corrugated rectangle.