quoin

noun

1. Any of the corner building blocks of a building, usually larger or more ornate than the surrounding blocks.

   “In Casterbridge there stood a noble pile, […] But evil days beset that domicile; The stately beauties of its roof and wall Passed into sordid hands. Condemned to fall Were cornice, quoin, and cove, And all that art had wove in antique style.”

2. The keystone of an arch.
3. (historical)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.

   “Next fit the quoins, using the “persuader” to squeeze in the pages, and tap up all around.”

4. (obsolete)A form of wedge used to prevent casks from moving.
5. A wedge of wood or iron put under the breech of heavy guns or the muzzle of siege-mortars to raise them to the proper level.
6. A number of apple varieties with a distinctive ribbed appearance, like corners of a coin.

verb

1. (transitive)To wedge or steady with quoins.