North Carolina Locksmith Practice Exam

A double cylinder deadlock is distinguished by its mechanism, which requires a key for operation from both sides of the door. This design is significant because it enhances security, particularly in situations where there might be glass panels near the door that could allow an intruder to reach through and unlock the door from the inside. With a key necessary to unlock the deadlock from either side, the risk of unauthorized access is reduced.

The other options do not accurately describe the characteristics of a double cylinder deadlock. Options that suggest it operates only from one side or features like built-in alarms or being made from plastic materials do not pertain to the fundamental design and function of a double cylinder deadlock. Thus, the correct identification of its dual-key operation is crucial for understanding how this type of lock serves its role in home and business security.