A Moment of Science

Under Lock and Key

Have you ever tried to pick a lock like in the movies with no luck? Well, you might have been better off knowing the inner workings of a lock.

Correct key with cyclinder

Photo: harry harris (flickr)

A key will open a lock only if its grooves raise each of the pins the correct length, allowing the cylinder to turn freely

Have you ever tried to pick a lock like in the movies with no luck? Well, lets learn about the inner workings of a lock to see how this works.

When you put a key in a lock and twist, you turn a part called the cylinder. The cylinder then turns a part called the cam, which makes the bolt slide in or out, depending on which way you turn.

Inside a lock are several shafts running through the cylinder and into the casing around the cylinder. Inside these shafts are pins of various lengths. Without a key inside, the bottom half of each pin rests inside the cylinder, while the top of the pin extends beyond the cylinder to the surrounding casing. This is what holds the cylinder in place. If you try to twist the cylinder without correctly moving the pins, the top pins will catch on the casing.

This is where the correct key comes in.

When you insert the right key, its notches raise the pins just enough so that the bottoms of the pins are aligned with the space between cylinder and casing. Since none of the pins are in both the cylinder and the casing at the same time, the cylinder turns freely.

Thus, when you pick a lock, you’re using a paper clip or whatever to push the pins up like the correct key would.

Stay Connected

What is RSS? RSS makes it possible to subscribe to a website's updates instead of visiting it by delivering new posts to your RSS reader automatically. Choose to receive some or all of the updates from A Moment of Science:

Support for Indiana Public Media Comes From

About A Moment of Science

Search A Moment of Science