A "casemate" was an armoured room in the side of a warship, from which a gun would fire. A typical casemate held a 6-inch gun, and had a front plate (forming part of the side of the ship), with thinner armour plates on the sides and rear, with a protected top and floor, and weighed about 20 tons (not including the gun and mounting). Casemates were similar in size to turrets; ships carrying them had them in pairs, one on each side of the ship.