What is the operating mechanism for a key-operated lock?

• A. Key
• B. Bolt
• C. Cylinder
• D. Gear

Answer: (C)

The operating mechanism in a key-operated lock is the lock cylinder. Inside the cylinder are pin stacks that align with the cuts on the key. When the correct key is inserted, the pins align at the shear line, allowing the plug to rotate inside the housing. That rotation is what moves the bolt, either retracting it to unlock or extending it to lock. The key provides the exact alignment, but the cylinder is the part that translates that alignment into turning motion and bolt movement. The bolt is the part that actually moves, but it’s driven by the cylinder’s rotation. Gears aren’t part of a typical key-operated lock, and the key is the input tool, not the mechanism itself.