A double-keyed deadlock, also known as a double-cylinder deadbolt, is a type of door lock that requires a key to operate from both the exterior and the interior sides of the door.
Understanding Double-Keyed Deadlocks
Unlike standard deadbolts that typically have a keyhole on the outside and a thumbturn or knob on the inside for easy operation, a double-keyed deadlock features keyholes on both sides. This means that to lock or unlock the door, regardless of whether you are inside or outside, you must use a key.
As per the reference provided:
- "A double-cylinder deadbolt has key-entry locks on both sides."
- This design choice means that "someone inside a house with a double-keyed deadbolt lock is staring at a keyhole in the spot where a person with a single-key deadbolt would see a knob."
- Therefore, "You'll need a key to lock and unlock the door from the interior and exterior."
This fundamental characteristic defines what a double-keyed deadlock is and how it functions compared to its single-keyed counterparts.
Key Characteristics
Here are the primary features of a double-keyed deadlock:
- Requires a key for both interior and exterior operation.
- Features a keyhole on the interior side instead of a traditional thumbturn.
- Provides locking/unlocking security from either direction.
Practical Insights and Considerations
While offering specific security benefits, double-keyed deadlocks also come with important practical considerations:
- Increased Security Against Forced Entry: If a door has glass panels or is located near a window, an intruder breaking the glass cannot simply reach in and turn a thumbturn to unlock the door. They would still need a key.
- Emergency Exit Challenge: A significant safety concern with double-keyed deadlocks is the requirement for a key to unlock the door from the inside. In emergencies like a fire, needing to locate a key before exiting can delay escape and potentially be dangerous. It is crucial to have a key readily accessible near the door at all times.
- Everyday Convenience: For day-to-day use, it is less convenient than a single-cylinder lock, which allows quick locking/unlocking from the inside without a key.
Choosing between a single-keyed and double-keyed deadlock often involves balancing security needs against ease of use and emergency preparedness. Building codes in some areas may restrict or prohibit the use of double-keyed deadbolts on exit doors, especially in residential settings, due to the emergency escape concerns.
