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Last edited 11 Dec 2024

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Mortice lock

A common lever-type mortice lock in the UK.

1 Introduction
2 History
3 Operation
4 Related articles on Designing Buildings

[edit] Introduction

A mortice lock (or mortise lock) is a lock that is carved or cut into a pocket on the side of a door or piece of furniture. This type of lock is sometimes used as a second lock for increased security and is commonly found in residential applications.

[edit] History

The mortice lock was commonly used in older buildings in the United States. Two of the country’s early presidents, Thomas Jefferson and James Madison both mentioned mortise locks as their security devices of choice. In 1788, Thomas Jefferson wrote to John Trumbull to request “mortise locks” on a carriage he wanted made to his specifications.

In 1798, James Madison included a reference to the devices (“mortise locks which I accordingly prefer”) in a letter to Jefferson. The letter followed with a review of matters of state. The discussion of locks came before the discussion of politics.

[edit] Operation

The locking body of a mortice lock is installed in the door, piece of furniture or other object while the box keep is installed in the facing frame. The mortice lock works by projecting its locking device (or lever) into the corresponding space on the facing side of the door frame or other object. A key is often used to operate the bolting mechanism and move it into the locked or unlocked position.

Mortice locks can create a layer of security on top of that which has been provided by standard cylindrical locks. Commonly available in deadlock and sashlock varieties, mortice locks are used in residential and commercial properties throughout the United States and Europe.

NB Code of practice: Hardware for fire and escape doors, Issue 5, published by DHF and GAI in November 2024, defines a deadlock as a: ‘Lock that contains only a deadbolt.’ Where a deadbolt is a: ‘Bolt that is operated in both directions by a key, handle and/or thumb turn.’