This is a interesting little article on the 'School of the 7 Bells', a underground school for training pickpockets. It gets its name from the bells sewn into the various pockets on a suit worn by a mannequin or the instrustor. Once you have mastered picking all the pockets on the suit without disturbing any of the bells, you graduate.
Google 'School of 7 Bells' for more information, below is but one article on the subject:
The School of the Seven Bells is a legendary, possibly apocryphal, and deliciously plausible school, said to be based in Colombia. Pickpocketing is largely a skilled combination of timing, and distraction, but South American pickpockets are particularly notorious.
There is, of course, an exam. Thieves-to-be are faced with a mannequin (or even a teacher) in a man’s suit, strewn with pockets, and rigged up with seven strategically-placed bells. They must pick the mark clean, without ringing a single bell.
The story changes with each telling: one version has it that the ‘diploma’ consists of a fake passport to the United States, and entry into one of the major American city crime gangs. The school may have closed, or even moved to Canada. Whatever the truth, the legend won’t die