quoin

The order to adjust the quoin in great-gun exercise; to depress the muzzle to point at an object below the level, in contradistinction to elevate.

From The Sailor's Word-Book An Alphabetical Digest of Nautical Terms, including Some More Especially Military and Scientific, but Useful to Seamen; as well as Archaisms of Early Voyagers, etc. by Sir Edward Belcher

I should have liked to see you when you were making for the side all top-heavy, and went flying over after the great quoin as you called it.

From Fitz the Filibuster by Harold Piffard

Mount Trafalgar made its first appearance in the form of a huge quoin or wedge, resting longitudinally upon the horizon, with its point towards the south-east.

From Discoveries in Australia, Volume 1. With an Account of the Coasts and Rivers Explored and Surveyed During The Voyage of H.M.S. Beagle, in the Years 1837-38-39-40-41-42-43. By Command of the Lords Commissioners of the Admiralty. Also a Narrative Of Captain Owen Stanley's Visits to the Islands in the Arafura Sea. by John Lort Stokes

When the inner or thick end of the quoin is fair with the end of the bed in place, the gun is level in the carriage; or horizontal, when the ship is upright.

From Ordnance Instructions for the United States Navy. 1866. Fourth edition. by United States. Navy Dept. Bureau of Ordnance

The piece of wood between the cheeks or brackets which, with the intervention of the quoin, supports the breech of the gun.

From The Sailor's Word-Book An Alphabetical Digest of Nautical Terms, including Some More Especially Military and Scientific, but Useful to Seamen; as well as Archaisms of Early Voyagers, etc. by Sir Edward Belcher