Bump proof locks are designed to resist the use of bump keys, which are special tools designed to open locks through brute force. These locks have specially designed "trap pins" that trigger when the lock is bumped, preventing the cylinder from turning and keeping the lock engaged.
Bump keys work by transmitting force to every pin in the lock at once, forcing them all above the shear line and allowing the lock to turn. This is in contrast to traditional lockpicking, where each pin is manipulated individually to free the cylinder and open the lock. Bump keys are much easier to use than lockpicks, requiring only a sharp blow instead of minutes of careful manipulation.