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The Locking Mechansim

Having looked at the history of padlocks and how and why they might be used, it's now time to understand how padlocks actually work. In the following pages we'll look at:


  • The locking mechanism used on Kasp™ padlocks

  • The pin tumbler mechanism - how a key is used to open and close the shackle

  • Combination locks - how a numbered dial is used to open and close the shackle


A Kasp™ padlock uses a key in a cylinder to open the lock. It's not complicated but it's very effective.

In this picture, you can see that the key is used to turn the cylinder. A mechanism on top of the cylinder withdraws the locking bars from the notches in the shackle, the shackle can then spring open.

What's missing here is some way of stopping the cylinder being turned without a key, so we add a locking mechanism. In Kasp™ padlocks we use what's known as a pin tumbler mechanism, which we'll look at now.

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