A pin tumbler lock is a tolerance-stacking problem wearing a security costume. The mechanism, why manufacturing imprecision is the exact thing that makes picking possible, how security pins fight back with false feedback, why Medeco's rotating-pin sidebar and Abloy's disc detainers are a different game entirely, and what real burglary data says locks actually defend against.
Tolerance-Stacking
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Mechanical Locks: Pin Tumblers and Why Picking Works