Heater shield

Geometrical construction of the Reuleaux triangle style of heater shield, for use as an heraldic escutcheon
An effigy of William Longespée the Younger (d. 1250) in Salisbury Cathedral, showing an early triangular heater shield
Heraldic roll of arms displaying heater-shaped heraldic shields or escutcheons. Hyghalmen Roll, Germany, late 15th century

The heater shield or heater-shaped shield is a form of European medieval shield, developing from the early medieval kite shield in the late 12th century in response to the declining importance of the shield in combat thanks to improvements in leg armour. The term is a neologism, created by Victorian antiquarians due to the shape's resemblance to a clothes iron. Examples are depicted in the great seal of Richard I and John, King of England.