In a pin-tumbler lock, the shear point is defined as what?

• A. The moment when the latch retracts from the strike.
• B. The moment at which the key is inserted.
• C. The point where the lock is rekeyed.
• D. The moment when all pins are aligned at the shear line, allowing the plug to rotate and the lock opens.

Answer: (D)

Pin-tumbler locks open when the pin stacks align at a boundary called the shear line. The key lifts each pin so the junction between the plug and the housing sits exactly at that line. When every pin sits across the shear line, the plug can rotate, and the lock opens. This moment—the pins aligned at the shear line to allow plug rotation—is the shear point. The other descriptions describe actions like retracting the latch, simply inserting a key, or rekeying, which don’t define the point where the plug is free to turn.