I saw this a while back on some other forum....
If you search youtube for "bump key", there are hundreds of videos on how to make and use bump keys for almost any lock. One kid shows how to bump a regular bike pad lock, I'm assuming to steal bikes!
There are locks out there that are bump key safe (make that, safer), meaning they are not able to be opened by a bump key at all (or not easiley opened by one).
Locks made by Medeco, Mul-T-Lock (sister companies), Schlage, and other manufacturers are advertised to be bump proof. Medeco and Schlage Primus locks are advertised as unbumpable due to sidebars that must be aligned to a specific depth to enable pin movement and pins chiseled at angles to further thwart bumping.[8][9]
http://en.wikipedia.org/wiki/Lock_bumpingThe above is a good article on how bump keys are made, how they work, and what to do to protect yourself against it.