The first suffix to be used was "C" for aircraft modified for launching from an aircraft catapult on a battleship. Before World War II, the suffixes were often consecutive, with many lacking defined meanings, and they were not often used. During the war, they came into wide use and were given defined meanings, but these were confusing and inconsistent, with letters being duplicated. For instance, the letter "A" was used both for deletion of the tailhook from an aircraft normally so equipped (e.g. the Douglas SBD-5A, used from land bases) and for addition of this equipment to a land-based aircraft; for amphibious versions of flying boats (e.g. the Consolidated PBY-5A); for armament added to a normally unarmed type; and for miscellaneous modifications (e.g. the aforementioned F4U-1A). The addition of a tailhook to a land-based aircraft could also be designated with a "C", e.g. the North American SNJ-5C, repeating the letter previously used for catapult-launched aircraft.