A lock is made up of levers (usually out of non-ferrous metals). Each lever needs to be lifted to a specific height by the key for the locking bolt to move. Typically, one cuts the belly of the lever away to various depths to provide different combinations. Or, they cut the gate in a different location to provide additional, or other varieties, for the lock. A lever will have pockets or gates through which the bolt stump moves during unlocking. Here are the most common lever locks you will find on modern doors today.

A 3 lever lock is a common type of lever lock but is generally used for low-security applications such as internal doors. As their tolerances are much lower, there are fewer combinations of essential available, so they are likely to unlock doors they shouldn’t.

A Mortise Sash lock incorporates a Deadbolt and a Latch bolt within the same case. A handle operates the Latch bolt, and the Deadbolt is opened and closed using a key. You can find this lock on most front doors, and many of them comply with British Standard BS3621. The Mortise Sash Locks are usually positioned below the centre of the door, so they miss the joint between the mid rail and latching style. They are also used in private flat entrance doors with an inside thumb turn deadlock. And on the side doors of houses usually supported with a pair of mortise security bolts. Finally, the Sash Locks apply the same security standards and features as the mortise deadbolt locks below.

Home insurance companies often require a five lever lock and are recommended by the police for home security. Most home insurers require at least one of the locks on your external doors. There are various grades, but the current (BS3621:2007) is usually needed for insurance purposes. Although the doors of many historic churches still carry an old wooden lock, you will find that many of them have also installed a modern 5-lever mortise lock alongside it to meet insurance requirements. Most BS3621 Locks have anti-pick devices built in to reduce the chance of lock picking, along with hardened bolts and anti-drill plates to reduce the risk of physical attack. Finally, you can find these locks with deadbolts, latches or a combination of both (when they’re called sash locks). Plus, you can get hook and claw bolts used for sliding doors and are fitted inside a lock pocket or amortise cut out of the door. These locks are ubiquitous, and the chances are that you have one or more of them on your gates. Additionally, they are available in two different sizes to suit the width of the door stile into which they are fitted. They are operated either by a cylinder key or a levered key.