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?

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Theres a bunch of little pins inside of the lock that keep the lock from turning. Putting in the right key moves them all out of the way. Putting in the wrong key wont move all the pins, and the lock won’t turn because they are still in the way.

They are all thin enough to fight through the keyhole, but the pattern on each key and the keyhole is different…which is why it won’t turn if it’s not the right match. You can put in a shit ton of keys, but if it’s not the right pattern it ain’t turning. I’m no expert though so…lol

There are two parts of a key. One is the grooves that run lengthwise down the body to create a profile that determines whether it fits into the keyhole. The other is the teeth on the key that determine whether it actually engages the tumblers inside the lock.

The actual locking mechanism is pins inside the lock for your standard tumbler lock. This is why one side of the key has a bunch of high and low points. Inside the lock are pins cut to various heights and those high and low points make it so they all like up at the same height right at what’s called the shear line (the point between the moving and stationary part of the lock).

The slot it fits into is called the warding. It *can* be useful for keeping out keys that aren’t meant for it (for example trying to put a Shlage key into a Kwikset KW1 lock, which by the way is the most common profile in America) but that’s not really their purpose. It’s there to make it harder to manipulate the lock with picks etc. a regular old rectangular hole would make it very easy to put lockpicking tools in there or pretty much anything like a paperclip or whatever, warding isn’t all that helpful with actual dedicated tools but even with those it takes someone who knows a bit about what they’re doing to pick it the old fashioned way.

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.

You can put a piece of uncooked **spaghetti** into the lock, and it won’t turn the lock.

Having the wrong wiggly pattern on the key doesn’t mean you can’t still put the thing into a keyhole.