How can a key that cannot unlock a door fit into the lock? But when you try to turn it to open the door, it does not open?

Question

Title.

In: Technology

Answer 1

There are only a handful of key blank design — a couple dozen or so. But the part that determines whether the key will open the door or not is what pins inside the lock that the key pushes down and how far. A lock has 5-7 pins and each can be set to 5-7 heights. The shape of the key pushes down each of those pins and only when they push down the pins to the exact right heights will the tumbler inside turn. An incorrect key will go in, push down pins, but not to the correct points where they can allow the tumbler to turn.