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How to Get Past A Lock

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Wikimedia Commons

Dan Lewis runs the popular daily newsletter Now I Know ("Learn Something New Every Day, By Email"). We've invited him to share some of his stories on mental_floss this week. To subscribe to his daily email, click here.

If your house has a standard door knob lock (a “pin tumbler lock”), the way it works is described graphically above (image via Wikipedia). The red and blue parts, combined, are called a “pin stack.” The blue pins, called “driver pins,” are spring-loaded, pushing the entire pin stack down. When there is not a key inserted into the lock, this prevents the lock from turning. But when a key is inserted, it pushes the red pins, called key pins, upward. If the key is the right one, the tops of the key pins (and therefore the bottom of the driver pins) form a straight line, called a shear line. With the pins now separated along this line, the key can turn, unlocking the door. It’s a neat, clean way to keep things safe.

Unless a thief or other miscreant knows about “lock bumping.”

Most pin tumbler locks are vulnerable to this crude, inexpensive-to-exploit flaw, which requires nothing more than a hammer and something called a “bump key.” The bump key is a special type of key with shallow, uniform teeth, allowing it to be inserted into the lock without risk of being thwarted by the presence of a deep pin stack. The bump key is inserted almost entirely into the lock, with one slot left exposed outside the mechanism. (The key will be pushed fully into place by the hammer rap to follow.) Once the bump key is properly inserted, the key pins rest on it while the driver pins, in turn, rest on the key pins with springs extended.

The villian then, ever so slightly, tries (at this point, in vain) to turn the key, but again, only slightly. The goal here is not to push the driver pins against their chambers, locking them in place, but to get the key going in the right direction when the magic happens in the next, and final, step. Our bogeyman takes the hammer and bangs it firmly against the key. The force exerted by the hammer is transferred to the key pins, and, like the desk top toy Newton’s Cradle, causes the key pins and driver pins to separate for a fraction of a second. And because the key is already being slightly turned, this momentary separation is more than enough time for the locking mechanism to be disabled. The key turns and the lock is unlocked.

Is your lock vulnerable? Most likely, yes, although many newer pin tumbler locks come with countermeasures, such as foam inserts which absorb the force from bumps.

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This Just In
Little Ross—a Tiny Island in Scotland With a Murderous History—Can Be Yours for $425,000
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Just off Scotland’s southwest coast sits the island of Little Ross. While picturesque, the remote speck of land comes with a tragic backstory: the 1960 murder of a lighthouse keeper, who died at the hands of a colleague. Now, decades after the tragedy made national headlines, the Independent reports that Little Ross is officially on the market and accepting offers over £325,000 (a little under $424,000).

The 29-acre island has a natural harbor, a rocky beach, and a craggy green coastline. There's also a six-bedroom cottage and several ramshackle barns, all of which are included in the purchase. A wind turbine and solar panels provide power (although everyone knows that good ghost stories are best enjoyed by candlelight).

What’s not for sale is the island’s 19th century lighthouse, the scene of lighthouse keeper Hugh Clarke’s 1960 murder. (His assistant, Robert Dickson, was found guilty, and received life imprisonment.)

“Since automation in the late 1960s the lighthouse no longer requires full-time staffing, and only the lighthouse and Sighting Tower are maintained by the Northern Lighthouse Board,” the island's listing states. “It is anticipated that the Northern Lighthouse Board and the purchasers will share the use, and future maintenance of the jetty wall.”

Since Ross Island is only accessible by boat or air, the listing advises that potential buyers be “proficient seamen” (or have access to a helicopter). Fit the bill, and in the market for an unconventional getaway? Check out the pictures below, or visit the island’s listing for more information.

The island of Little Ross, which sits off the Meikle Ross headland on Scotland’s south coast.
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The island of Little Ross, which sits off the Meikle Ross headland on Scotland’s south coast.
Galbraith

[h/t Independent]

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crime
The Reason Police Officers Tap Your Taillight When They Pull You Over
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Asking a driver for their license and registration is common procedure from police officers during traffic stops. There’s another practice that was once standard across the force but is more of a mystery to the people being pulled over: While approaching a driver’s window, officers will sometimes touch a car's taillight. It's a behavior that dates back decades, though there's no reason to be concerned if it happens at your next traffic stop.

Before cameras were installed on the dashboards of most police cars, tapping the taillight was an inconspicuous way for officers to leave behind evidence of the encounter, according to The Law Dictionary. If something were to happen to the officer during the traffic stop, their interaction with the driver could be traced back to the fingerprints left on the vehicle. This would help other police officers track down a missing member of the force even without video proof of a crime.

The action also started as a way for officers to spook drivers before reaching their window. A pulled-over motorist with a car full of illegal drugs or weapons might scramble to hide any incriminating materials before the officer arrives. The surprise of hearing a knock on their taillight might disrupt this process, increasing their likelihood of getting caught.

Today the risks of this strategy are thought to outweigh the benefits. Touching a taillight poses an unnecessary distraction for officers, not to mention it can give away their position, making them more vulnerable to foul play. And with dash cams now standard in most squad cars, documenting each incident with fingerprints isn’t as necessary as it once was. It’s for these reasons that some police agencies now discourage taillight tapping. But if you see it at your next traffic stop, that doesn’t mean the officer is extra suspicious of you—just that it’s a hard habit to break.

[h/t The Law Dictionary]

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