The 5 lever lock is a type of Lever tumbler lock often required for home insurance and often recommended by the police for home security. There are various grades but the current British Standard (BS3621:2007) is usually required for insurance purposes. The lever mechanism is really only seen in the UK and some parts of Scandinavia, and locks using this form of mechanism are frequently referred to as Chubb locks although there are a great many manufacturers. BS3621:2007 requires a bolt throw of 20 mm rather than the 14 mm of the earlier British Standard. Most BS3621 locks have anti pick devices built in to reduce the chance of lock picking.
A flat, usually non-ferrous metal, shaped double-acting movable part in a lock. Usually pivoted, but sometimes sliding. The levers in a lock have to be moved by the key to operate the lock. Typically, the belly of the lever is cut away to various depths to provide different combinations, or the gate is cut in a different location, to provide differs. A lever will have pockets or gates through which the bolt stump moves during unlocking. Synonymous with "detainer".