The heater shield or heater-shaped shield is a form of European medieval shield

Shield

A shield is a type of personal armor, meant to intercept attacks, either by stopping projectiles such as arrows or redirecting a hit from a sword, mace or battle axe to the side of the shield-bearer....

, developing from the early medieval kite shield

Kite shield

A kite shield was a distinct type of shield from the 10th–12th centuries. It was either a reverse teardrop shape or later on, flat-topped. The tapering point extended down to either a distinct or rounded point...

 in ca. the mid 13th century.

The term is a neologism, created by Victorian antiquarians due to the shape's resemblance to a clothes iron

Iron (appliance)

A clothes iron, also referred to as simply an iron, is a small appliance used in ironing to remove wrinkles from fabric.Ironing works by loosening the ties between the long chains of molecules that exist in polymer fiber materials. With the heat and the weight of the ironing plate, the fibers are...

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Smaller than the kite shield, it was more manageable and could be used either mounted or on foot. From the 15th century, it evolved into highly specialized jousting

Jousting

Jousting is a martial game or hastilude between two knights mounted on horses and using lances, often as part of a tournament.Jousting emerged in the High Middle Ages based on the military use of the lance by heavy cavalry. The first camels tournament was staged in 1066, but jousting itself did not...

 shields, often a bouche containing a notch or "mouth" for the lance to pass through. As plate armor began to cover more and more of the body, the shield grew correspondingly smaller, until by the mid 14th century, it was hardly seen at all outside of the tournament.
Heater shields were typically made from thin wood

Wood

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 overlaid with leather

Leather

Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...

. Some shields, such as that of Edward, the Black Prince

Edward, the Black Prince

Edward of Woodstock, Prince of Wales, Duke of Cornwall, Prince of Aquitaine, KG was the eldest son of King Edward III of England and his wife Philippa of Hainault as well as father to King Richard II of England....

 from his tomb in Canterbury Cathedral

Canterbury Cathedral

Canterbury Cathedral in Canterbury, Kent, is one of the oldest and most famous Christian structures in England and forms part of a World Heritage Site....

, incorporated additional layers of gesso

Gesso

Gesso is a white paint mixture consisting of a binder mixed with chalk, gypsum, pigment, or any combination of these...

, canvas

Canvas

Canvas is an extremely heavy-duty plain-woven fabric used for making sails, tents, marquees, backpacks, and other items for which sturdiness is required. It is also popularly used by artists as a painting surface, typically stretched across a wooden frame...

, and/or parchment

Parchment

Parchment is a thin material made from calfskin, sheepskin or goatskin, often split. Its most common use was as a material for writing on, for documents, notes, or the pages of a book, codex or manuscript. It is distinct from leather in that parchment is limed but not tanned; therefore, it is very...

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