The heater shield was a shield used in the later Middle Ages following the decline of the Kite shield.
The heater shield was a medium-sized triangluar shield that developed from the kite shield in the middle of the 13th century. It was much more manageable than a kite shield, and could be used both mounted and on foot. However, it was easily large enough to block blows from most weapons, and provided ample protection for the wielder. IUt was often made from wood overlaid with leather.
The heater shield, as a medium sized shield, would have been able to not only deflect but also outright block the blows of an opponent.