In the “good old days” of bicycling, bicyclists had to protect their bikes with flimsy chains and cables that a determined thief with a bolt-cutter could bypass in just a few seconds. Many bikes were stolen.

But then came the hardened-steel U-shaped Krypto Lock, a lock that laughed at puny bolt-cutters. It would take either liquid nitrogen or construction equipment to get it to come off—neither of which your typical bicycle thief was likely to have at his disposal. They were immediately widely-adopted, and not just for bicycles, either; I’ve heard that they are often used by protesters to lock themselves to buildings or heavy equipment to make it harder for the cops to haul them away.

Unfortunately, a chain is only as strong as its weakest link—and a lock, no matter how tough, is only as strong as its latch mechanism. A discussion from a bicycling web forum has shown up, linked on BoingBoing, demonstrating that at least certain models of Krypto Lock can be opened with a common Bic ball-point pen. And it’s not just words alone—there are two Quicktime movies (here and here) actually demonstrating it being done.

The movies are amazing. All it takes is one of those standard white plastic ball-point pens that you can buy in packs of 10 for $1, with the plug at one end of the tube taken out. Stick the tube in the keyhole, wiggle it around, and click, open it comes.

Looks like it may be time for bikers to get another lock.