quoin

verb

masonry blocks at the corner of a wall
a solid exterior angle (as of a building)
the keystone or a voussoir of an arch
a wooden or expandable metal block used by printers to lock up a form within a chase
a wedge for raising the level of a gun barrel or for keeping it from rolling

Pronunciation: /k(w)ɔɪn/

Etymology: Variant of coin; compare coign.

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.”
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.
“Next fit the quoins, using the “persuader” to squeeze in the pages, and tap up all around.”
A form of wedge used to prevent casks from moving.
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.
A number of apple varieties with a distinctive ribbed appearance, like corners of a coin.

Etymology: Variant of coin; compare coign.