Lexicon:Quoin

From WikiPOBia

A strong wedge, generally of wood, placed under the breach of a gun to control elevation. The sloping edge of the quoin ran parallel to the gun's barrel. Using a handspike as a lever, the breach of the gun would be raised to lift it from the quoin. If the gunner moved the quoin in towards the mouth of the gun, the breach would be higher when it was eased down and the mouth of the gun lower. If the quoin were moved further back from the mouth, the breach would rest lower, raising the mouth.