Definition from Wiktionary, the free dictionary
quoin (plural quoins)
- Any of the corner building blocks of a building, usually larger or more ornate than the surrounding blocks.
- The keystone of an arch.
- A metal wedge which fits into the space between the type and the edge of a chase, and is tightened to fix the metal type in place.
- (obsolete, nautical) A form of wedge used to prevent casks from moving
- (corner block of a building): cornerstone