Locks are the main line of defense that most people use to protect their valuables. Here's a roundup of the HowStuffWorks articles that discuss different types of locks:

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lock picking
How Lock Picking Works
Lock picking allows people to open locks with only a few tools. Learn how to pick a lock,
how pin and tumbler locks work, and about types of keys, re-keying and master keys. Then test your skills with our Lock Picking Quiz!
combination lock

How Combination Locks Work
Combination locks use wheel packs to set the combination inside the lock, a design that has stayed the same for the past 100 years. Learn about combination locks and see pictures of the inside of a combination lock.
inside lock

Inside a Combination Lock
If you have used a combination lock before, you know the drill: "Turn the dial clockwise two full rotations to the first number of the combination. Then turn it counter-clockwise past the first number to the second number. Then turn the dial clockwise to the third number and the lock will open." But what's happening when you do that?
safe

How Safecracking Works
In the movies, master thieves and spies can deftly defeat a safe in a matter of seconds using little more than steady hands and a good ear. Safecracking isn't really that easy of course, but expert safecrackers really can get through just about any lock mechanism. It's a matter of having the right tools, the right skills and plenty of patience.
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fingerprint scanner

How Fingerprint Scanners Work
In this article, we'll examine the secrets behind this exciting development in law enforcement and identity security. We'll also see how fingerprint scanner security systems stack up to conventional password and identity card systems, and find out how they can fail.