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What type of deadbolt can be operated by a key from both sides?
Single Cylinder Deadlock
Double Cylinder Deadlock
Chain Lock
Deadlatch
The correct answer is: Double Cylinder Deadlock
The correct choice is the double cylinder deadlock. This type of deadbolt can be operated by a key from both sides, which enhances security by preventing unauthorized access through a door that has glass panels or windows nearby, as a person cannot simply reach in to unlock it from the inside. In contrast, a single cylinder deadlock typically allows for key operation from the outside, but has a thumb turn on the inside, which can be easily manipulated without a key. Chain locks and deadlatches also do not provide a key-operated function from both sides, as they are designed for different purposes and mechanisms, primarily focusing on convenience or additional security features rather than the dual-key operation that characterizes the double cylinder deadlock.