The Collaborative International Dictionary
Capsquare \Cap"*square\, n. (Gun.) A metal covering plate which passes over the trunnions of a cannon, and holds it in place.
Wiktionary
n. A metal plate that covers the trunnions of a cannon and holds it in place.
Wikipedia
In artillery, capsquares, or capsquires, are strong plates of iron which come over the trunnions of a cannon, keeping it in its carriage. They are fastened by hinges to the paizeplate, so that it could be lifted up and down. They form a part of an arch in the middle, to receive a third part of the thickness of the trunnions; for two thirds of them are let into the carriage, and the other end is fastened by two iron wedges, which are called the forelocks, and keys.
Category:Carriages and mountings
Usage examples of "capsquare".
The barrels had to be shifted on the carriages from their travelling position into the fighting stance, then trunnions must be clamped with iron capsquares as powder and grapeshot were rammed into cold muzzles.
Doubtless Bampfylde's fire had weakened the capsquare and now the twelve-pounder was as good as useless.
Its capsquare was broken, but the barrel was charged with the last of the garrison's dry powder and rammed with metal scraps, stone fragments, and rusty nails.