shield

A geological term for a large region of stable continental crust, usually Precambrian in age and forming the core of a continental land mass. It is predominantly composed of metamorphic and igneous rocks.

The term often refers to a device that is held in the hand, as opposed to armour or a bullet proof vest.
The oldest form of shield was a protection used to block attacks by hand weapons, such as swords, axes and maces, and missiles, like spears and arrows. Sometimes shields were made of metal, but wood or animal hide construction was much more common; Many surviving examples of metal shields are generally felt to be ceremonial rather than practical, for example the Yetholm-type shields of the bronze age or the iron age Battersea shield.

Size and weight varied greatly, lightly armoured warriors relying on speed and surprise would generally carry light shields that were either small or thin. Heavy troops might be equipped with large heavy shields that could protect most of the body. During the 14th-13th century BCE, the Sards or Shardana, working as mercenaries for the Egyptian pharaoh Ramses II, utilized either large or small round shields against the Hittites. The Ancient Greek hoplites used a round, bowl-shaped wooden shield called an aspis. Free standing shields called pavises were used by medieval crossbowmen who needed protection while reloading.

The heavily armoured Roman legionaries carried large rectangular shields (scuta) that could provide far more protection, but made swift movement more difficult. Famously the Romans used their shields to create a tortoise-like formation called a testudo in which entire groups of soldiers would be enclosed in an armoured box.

Many ancient shield designs featured incuts of one sort of another. This was done to accommodate the shaft of a spear thus facilitating tactics requiring the soldiers to stand close together forming a wall of shields.

In the early European Middle Ages there were so-called kite shields; Tower shields were common among front-line troops, often spearmen with shorter spears. As personal body armour improved, knight's shields became smaller, leading to the familiar "heater" style. Both kite and heater style shields were made of several layers of laminated wood, with a gentle curve in cross section. The heater style inspired the shape of the heraldic shield that is still used today.

In time, some armoured foot knights gave up shields entirely in favour of mobility and two-handed weapons. The buckler is a small round shield, typically between 8 and 16 inches in diameter. The buckler was one of very few types of shield that was usually made of metal. Bucklers are also called punching shields as soldiers would commonly bash a foe who's helmet left the face unprotected in the nose to stun and disorient him before a sword strike. Thus it was lighter than the tower shield and hence easier for the bearer to wield a weapon without sacrificing protection.

Shields continued in use even after gunpowder powered weapons made them nearly obsolete in the battlefield. In the 18th century, the Scottish clans used a small, heavy, round shield called a targe that was partially effective against the firearms of the time.

In the 19th century, non-industrial cultures with little access to guns were still using shields. Zulu warriors carried large lightweight shields made from a single ox hide supported by a wooden spine, these were called Ishlangu.

Shields for protection from armed attack are still used by many police forces around the world. Synthetic riot shields are normally transparent, allowing full use of the shield without obstructing vision. Metal riot shields often have a small window at eye level for this purpose.

The second type of modern police shield is typically manufactured from advanced synthetics such as kevlar and are designed to be bulletproof, or at least bullet resistant.

Many non-martial devices also employ shields.

Science fiction writers have imagined many futuristic shields, usually using force fields.