\Quoin\, n. [See {Coin}, and cf. {Coigne}.]
1. (Arch.) Originally, a solid exterior angle, as of a
   building; now, commonly, one of the selected pieces of
   material by which the corner is marked.
Note: In stone, the quoins consist of blocks larger than
      those used in the rest of the building, and cut to
      dimension. In brickwork, quoins consist of groups or
      masses of brick laid together, and in a certain
      imitation of quoins of stone.
2. A wedgelike piece of stone, wood metal, or other material,
   used for various purposes, as:
   (a) (Masonry) to support and steady a stone.
   (b) (Gun.) To support the breech of a cannon.
   (c) (Print.) To wedge or lock up a form within a chase.
   (d) (Naut.) To prevent casks from rolling.
{Hollow quoin}. See under {Hollow}.
{Quoin post} (Canals), the post of a lock gate which abuts
   against the wall.