Today I completely terrified a friend of mine, who happens to be a Close Protection Professional. (That's a bodyguard to you and me.)

How did I freak him out? Did I petrify him with my awesome marksmanship ability? Scare him half to death with my martial arts skills? Intimidate him with a dazzling new self-defense theory? None of the above, I'm afraid.

I got into his brand new "impregnable" steel-plated front door in under five seconds. I didn't have a key, I didn't "pick" the lock, and I didn't damage the door or lock in any way. The door was locked securely before I started, and nobody let me in.

It sounds like the beginning of one of those trick riddles, huh? You know the type; a man is sitting in an empty room with no doors and no windows, how does he escape? But it's not a riddle. It is, however, a trick. A very sneaky, very scary trick than can allow you to bypass ninety percent of the world's locks in seconds—and with very little skill!

Let me fill you in on the background of the story before telling you about the technique I used. My buddy knows how paranoid I am about security, so he was proud to show me his new stainless steel "super door" he's fitted at the front of his house. He lives on the outskirts of a pretty rough neighborhood and was excited as he pointed out that the door (which cost him hundreds of dollars) was totally bullet proof and barge proof. He locked the door and stood back in admiration. "Nobody's getting through THAT unless I say so!" He beamed.

Antagonistic bastard that I am, I took my special key from its permanent location on my keychain, and started tapping it briskly with the solid end of the keychain, putting turning pressure on the handle as I did so. After just seconds, bingo—the lock popped open, the handle turned, and I effortlessly opened his "super door". It might as well not have been there.

Those of you in the know will recognize the description given above as the technique called "lock bumping". This requires a special blank "bump key"—you can make one from any cylinder lock key by filing down the teeth to the level of the key shoulder. Alternatively, you can buy them ready prepared from the internet.

Lock bumping works using the laws of physics. Most locks are pin tumbler locks; cylindrical pin tumbler locks were patented by Yale over a century and a half ago, and the design has hardly changed to this day. These locks work by securing a cylinder (called a plug) with spring-loaded pins of different sizes. In theory, only the correct key will push these pins slightly beyond the border of the plug (to a point called the shear point). When this happens, the plug can be freely turned and the lock opens.

Inserting a bump key with the correct profile will cause the stumps of the key to come into gentle contact with the tips of these spring-loaded pins. When the extruding end of the bump key is struck, the key's metal transmits force along its length, which causes the pins to jump away from the key in unison for a split second.

This phenomenon is not unlike the desk toy known as "Newton's Cradle", where metal spheres strike one another, forcing the end balls to swing away. The principle is the same—Newton's Third Law of Motion (i.e., "every action has an equal and opposite reaction").

When the pins jump up, they jump clear of the shear point, and the plug is able to move freely—in other words, you can turn the lock, opening it.

Lock bumping requires very little skill—it's more accurate to describe it as a knack—once you have it, you can bump virtually any cylinder lock with just a few tries. It's fascinating to know the theory, but you can do it even with no knowledge of lock mechanics; I've seen little kids do it, in fact.

Security bypass skills are an important tool in your technical arsenal. Combat and sabotage are obviously useful applications. Getting inside an enemy location covertly can give you a massive tactical edge in an extreme situation, maybe in cases where the law can't help you. In addition, during periods of anarchy or social breakdown, knowledge of how to get inside storage areas for requisitioning food and other supplies can mean the difference between life and death. So bypassing locks can also be a survival skill. I've spent literally years developing my lock picking techniques, but I'd advise anybody to learn lock bumping before the art of lock picking. It's infinitely easier and quicker, and leaves no sign of forced entry—even to forensics investigators.

If you do want to learn more about bumping, you can read the best essay I've ever found on the topic here. It's also a good idea to watch an illustrative animation, which will make the mechanics of bumping much easier to grasp than is the case with written text. There's a helpful video here. If you want to get hold of some bump keys to train with, www.bumpkey.us have a wide selection of different types for different locks.

It's also a good idea to be aware of lock bumping from a home security perspective. One way to make your base immune is to fit bump-proof locks (rotating disk locks, electronic locks and magnetic-type locks are invulnerable to bumping). If you can't afford to change your locks, at least having internal bolts will prevent a lock bumper from getting into your house while you're inside (although not when you've locked your door from the outside).

Knowledge is power!