Yale Locks BS2 Nightlatch British Standard Lock 40mm Backset Chrome Finish VisiYale's maximum security BS2 nightlatches are British Standard approved to ensure the highest level of security for timber external doors. They are Kitemarked to BS 3621: 2007 and are recommended by insurance companies. The lock is key operated from the outside and both key and lever handle operation from the inside with the internal handle being lockable for increased security. The latch automatically deadlocks on closing the door and the snib