 These could be warships carrying their principal batteries of carriage-mounted guns on a single deck or on two decks (with further smaller carriage-mounted guns usually carried on the forecastle and quarterdeck of the vessel).The term was generally used for ships too small to stand in the line of battle, although early line-of-battle ships were frequently referred to as frigates when they were built for speed.In the 18th century, frigates were full-rigged ships, that is square-rigged on all three masts, they were built for speed and handiness, had a lighter armament than a ship of the line, and were used for patrolling and escort.