How door locks work
![]() |
This iron metalwork object is a 16th century rim lock and key from France. |
Contents |
[edit] Introduction
A door lock is a mechanism used for security purposes - preventing a door from being opened by unauthorised people. There are many different types of door locks. Two of the most basic types of locks are rim locks and cylinder locks.
[edit] Rim locks
One of the oldest types of locks, the rim lock uses a bolt and key to secure the door. The bolt in the lock is moved when the correct key is inserted into the mechanism and turned. This action presses the tumbler - which is kept in place by a spring - up, and frees the bolt.
Next, the key bit engages with the corresponding notch under the bolt. Turning the key moves the bolt until the catch of the tumbler fits into next notch on the top of the bolt.
In simple locks, this completes the locking action. Greater safety is provided by a lock having not one, but several tumblers.
[edit] Cylinder locks
A cylinder lock uses a rotating mounted plug. When locked, the cylinder is held in place by several pin tumblers that have been moved into the proper position by springs. This allows the pins to fit into corresponding holes in the cylinder and keep the cylinder from moving.
A key is then inserted into the lock, which raises the pins so their tops move to a position that corresponds to the top of the outer surface of the cylinder. When the different segments of the tumbler are not connected, the cylinder can move freely when the key is turned. This allows the bolt to move and unlocks the door.
Another type of cylinder lock is the disc tumbler lock. This type of lock uses movable discs instead of pins to lock the cylinder.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
The Building Safety Forum at the Installershow 2025
With speakers confirmed for 24 June as part of Building Safety Week.
The UK’s largest air pollution campaign.
Future Homes Standard, now includes solar, but what else?
Will the new standard, due to in the Autumn, go far enough in terms of performance ?
BSRIA Briefing: Cleaner Air, Better tomorrow
A look back at issues relating to inside and outside air quality, discussed during the BSRIA briefing in 2023.
Restoring Abbotsford's hothouse
Bringing the writer Walter Scott's garden to life.
Reflections on the spending review with CIAT.
Retired firefighter cycles world to raise Grenfell funds
Leaving on 14 June 2025 Stephen will raise money for youth and schools through the Grenfell Foundation.
Key points for construction at a glance with industry reactions.
Functionality, visibility and sustainability
The simpler approach to specification.
Architects, architecture, buildings, and inspiration in film
The close ties between makers and the movies, with our long list of suggested viewing.
SELECT three-point plan for action issued to MSPs
Call for Scottish regulation, green skills and recognition of electrotechnical industry as part of a manifesto for Scottish Parliamentary elections.
UCEM becomes the University of the Built Environment
Major milestone in its 106-year history, follows recent merger with London School of Architecture (LSE).
Professional practical experience for Architects in training
The long process to transform the nature of education and professional practical experience in the Architecture profession following recent reports.
A people-first approach to retrofit
Moving away from the destructive paradigm of fabric-first.
International Electrician Day, 10 June 2025
Celebrating the role of electrical engineers from André-Marie Amperè, today and for the future.
New guide for clients launched at Houses of Parliament
'There has never been a more important time for clients to step up and ...ask the right questions'
The impact of recycled slate tiles
Innovation across the decades.
EPC changes for existing buildings
Changes and their context as the new RdSAP methodology comes into use from 15 June.