#LearnLockpickingWithAlice lesson 6: What goes on inside a lock?

A (typical pin tumbler) lock consists of a pretty simple mechanism. Pairs of pins—the driver and key pins—are pushed by a spring, such that the driver pins block the core of the lock from rotating. When a key is inserted, it raises the pin-stacks so that the driver pin is above the shear line between the core and the lock housing, and they key pin is below it. Key pins are different lengths to compliment the bitting of the key, so that they all end up being the same height when resting on the cuts in the key.

In picking a lock, we simulate the key by manipulating the pins manually.

Locks are only pickable because manufacturing is imperfect. *Ideally* the pin chambers would be perfectly identical and in a perfectly straight line. *Ideally* the pins would be perfectly smooth and identical in all but length. But that's never the case. And we can use that fact to our advantage.

When we apply rotational force to the core of the lock with our turning tool, it causes the pin-stacks to pinch between the core and the housing. The pin closest to the direction we're turning will get pinched the hardest. That's the one we're looking for. When we lift that pin with our pick, it scrapes against the pin chamber until it reaches the shear line. Once it's set correctly, the next closest pin will bind, and so on. It's the same pinching that causes the set pins to stay in place—they rest on the lip of the core's chamber. Once all the pins are set, nothing is blocking the core from turning, and *click* the lock opens.

When you lift a pin too high, you "overset" it, which means the key pin is now the thing being pinched, rather than the driver pin. This'll result in a mushy, dead feeling in the pin. It'll go up, but won't spring or fall back down. It also means other pins won't bind, so everything just feels kind of lifeless in the core (like we do under capitalism).

If you *ease* off the tension, then eventually a pin will drop back down. With any luck, it's the overset one. Reapply tension and poke around to see if a pin is binding nicely If not, ease off tension again until another pin drops. This is how you recover from a misstep while picking. If you have to do this more than once or twice, consider dropping all the pins and starting over—because you've probably lost your mental image of the lock's state and it'll be better to start clean.