 It works almost as well as actually having a key, and a set of ten rapping keys can make the criminals capable of opening 90% of common tumbler locks.High-quality locks may be more vulnerable to bumping unless they employ specific countermeasures.More precise manufacturing tolerances within the cylinder make bumping easier because the mechanical tolerances of the lock are smaller, which means there is less loss of force in other directions and mostly pins move more freely and smoothly.