The Collaborative International Dictionary
Gige \Gige\ (g[i^]j or g[=e]j), Guige \Guige\, n. [OF. guide,
guiche.] (Anc. Armor)
The leather strap by which the shield of a knight was slung
across the shoulder, or across the neck and shoulder.
--Meyrick (Ancient Armor).
Guige \Guige\ (g[i^]j or g[=e]j), n. [Obs.] See Gige.
n. A strap attached to a shield, used to hang the shield over the shoulder or from the neck.
A guige is a long strap, typically made of leather, used to hang a shield on the shoulder or neck when not in use. Used in combat, it freed a soldier to use a weapon requiring two hands (or a weapon in each hand) without discarding the shield; the shield could then be easily retrieved when needed.
Some guiges had a buckle to adjust the length. A guige could be attached to the shield anywhere along its rim, and could run horizontally, vertically, or diagonally across the diameter of the shield.
Most information about the usage of guiges comes from various Medieval works of art, such as the Bayeux Tapestry.