A centre-boss shield was a type of round or oblong shield common in period. It has called a centre-boss because of the single central grip, protected by a metal boss. Most centre-boss shields actually had a hole in the centre with the grip flush to the shield, with the protective boss projecting outward from the shield face itself. There is some speculation that historical some may have had a slight conical shape to the shield.
Historically these shields metal bosses in the centre riveted to the wooden planked body which could be up to 95cm in diameter. Behind the shield is a wooden or metal crossbar to act as a handle. The face and back of the shield could be covered in leather stuffed with grass and painted.
Centre-boss shields are handled very differently from other shield types (such as the kite shield or the heater shield) which are strapped to the arm. Tending to be smaller and more light-weight, a centre-boss shield is "punched" towards an incoming blow.