quoin

noun

• 1an external angle of a wall or building.
• (also quoin stone) any of the stones or bricks forming an external angle of a wall or building; a cornerstone.

• 2 Printing a wedge or expanding mechanical device used for locking a letterpress form into a chase.

• 3a wedge for raising the level of a gun barrel or for keeping it from rolling.

verb

• 1provide (a wall) with quoins or corners.

• 2 Printing lock up (a form) with a quoin.