The classic “knight in shining armor” medieval shield evolved from a roughly triangular-shaped Norman shield. Our earliest reference to this Norman-type shield is on the Bayeux tapestry, which shows several images of a shield shaped like an upside-down water droplet.
The Norman shield was used for several centuries, due to its effectiveness at defense, especially for a rider on horseback. The long, narrow shape easily covered the rider’s side, and guarded against the lance strikes of any opposing horsemen.
Unlike the Viking or Anglo-Saxon shields, the Norman shield was quite securely fastened to the arm of the user. Three straps on the shield, called enarmes, kept the shield on the left arm of the wearer. Another set of straps, called the guige, wrapped around the neck and shoulders of the wearer, to allow the weight to hang there while the arm was used for another task.
Over time, this shield turned into the classic medieval shield. The medieval shield looked like a triangle with two slightly curved sides, and was made out of wood with a covering of leather, cloth, or parchment. One or both sides were painted to represent the house of the knight who carried it. This practice became complicated over time, due to the marriages of different houses and the large number of knights, and turned into an art all of its own, called heraldry.
In keeping with the style of the Norman shield, the medieval shield also had the enarmes and guige that allowed greater flexibility and protection at the same time. This was essential, as the protection against lances was paramount in the medieval tournaments.
Even as styles and sizes changed, the basic construction of the ancient shield remained the same through the middle ages. So did its function. And although the construction of the shield has long since passed, the function of a shield hasn’t even changed today.