A buckler (French bouclier 'shield', from Old French bocle, boucle 'boss') 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 during the Medieval and Renaissance periods. 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 as in Hans Talhoffer's Fechtbücher or serrated rings around the boss as in one example in the Wallace Collection. The second major form is a corrugated rectangle as suggested by Achille Marozzo in his Opera Nova.