Yale's maximum security BS1 nightlatches are British Standard approved to ensure the highest level of security for timber external doors. They are Kitemarked to BS 36212007 and are recommended by insurance companies. These security nightlatches have been approved by the Police Secured by Design initiative. The Yale 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 function enables the latch to be held back. The lock uses a 6-pin high-performance cylinder and has a 20mm bolt which is anti-carding. It also has a 15-year guarantee. The BS1 nightlatches have a 60mm backset, this is the measurement from the edge of the door to the centre of the keyhole. Locks with a 40mm backset are normally used where there is restricted space, such as on a glass panelled door Case Width 90mm Case Height 90mm Case Depth 33mm This Yale PBS1CH has a hardened case finished in polished chrome and the cylinder is also finished in Polished Chrome Supplied with 2 x keys