Nightlatch is a locking mechanism commonly used for external doors, characterised by its ability to be locked from the outside with a key and from the inside with a snib, a small lever or knob. This type of lock, often referred to as a 'rim lock', is mounted on the surface of the door rather than being embedded within it, distinguishing it from more complex mortise locks. The design ensures ease of exit in emergency situations, as it typically allows for quick unlocking from the inside without a key.
The lock's construction utilises a spring-loaded latch mechanism that automatically engages the doorframe when the door is closed, providing a basic level of security. Advanced models may include features such as deadlocking, which prevents the latch from being forced open from the outside, or auto-deadlocking, which enhances security by automatically engaging a deadbolt upon closing. Nightlatches are available in a variety of finishes and styles, catering to both functional security needs and aesthetic preferences. Their adaptability to diverse door types and the minimal installation effort required make them a favored choice in residential settings. The lock's utility and design reflect its role as a first line of defense, offering user-friendly security while complementing the architectural integrity of entryways.