A coign (also written
quoin,
coigne, and
coin) is the exterior angle of a
wall,
tower,
keep, etc. and all component
stones of the
angle. Coign stones tend to be larger than the stones of the wall proper, and lend an
aesthetic to the
structure. A coign is also the term for a
keystone in an arched doorway. The origin of the word is from the
French coin, meaning "
corner".
In printwork, a coign is a wooden or metal wedge to lock the type in a chase.
In the context of missle weapons, a coign is a wedge used to raise the angle of a gun or other projectile weapon.