ERA Fortress British Standard 3621 5 Lever Maximum Security Deadlocks are recommended for External timber and composite doors. The BS 3621 standard is recognised as giving the maximum protection for home and commercial use. The laminated steel Deadbolt helps to prevent hacksaw attacks. The Deadbolt has a 20mm throw for greater security. Hardened steel plates on the casing prevent drill attacks. The 5 Lever mechanism is designed to prevent lock picking. ERA Fortress locks are ideal for use in new doors or upgrading security from 2 and 3 lever door locks. Deadlocks do not require door handles.