Lock bumping is a fast and unobtrusive way for thieves to open a door without leaving a sign of forced entry. All it takes is a modified key that fits in the lock slot. Tapping the key with a hammer "bumps" the locking pins out of the way so that the cylinder can turn and retract the bolt. To thwart the bad guys, manufacturers have developed bump-resistant dead bolts, like Kwikset's
SmartKey with BumpGuard (shown), about $30.