The combination of a safe or vault has often been learned by these burglars by obtaining an entrance to the banking house after banking hours, removing the dial of the combination and placing a sheet of tin foil behind it. Then, replacing the dial, the turning of the combination in opening or closing makes the impression of letters or numbers on the soft foil, which is removed by the burglar at the first chance he has to get into the banking house. Having the combination impressed on the tin foil, he and his accomplices open the vault or safe, secure the contents, and then often change or put out of order the combination, so the doors of the vault or safe cannot be opened for some hours after the regular time for opening, and then only by an expert of that particular safe company. This, of course, gives the thieves several hours of valuable time in which to effect their escape. The tools required by the mechanical burglar who forces open safes are the air pump, putty, powder, fuse, sectional jimmy, steel drills, diamond drills, copper sledges, steel-faced sledges (leather covered), lamp and blow pipe, jack screw, wedges, dynamite and syringe, brace with box slide, feed screw drills, steel punches, small bellows, blank steel keys, skeleton keys, nippers, dark lantern, twine and screw eyes. The latest, most dangerous set of tools manufactured is the second power in mechanics--the screw. The method of work with the screw is to first rig a brace, and then drill a hole in the safe, cut a thread in the hole and then insert a female screw. Then, with a long steel screw with a handle so long that two men can turn it, the screw is inserted in the female screw, and by turning it goes in until it strikes the back of the safe. Then either the back or the front must give way. In nearly all cases it is the latter, as that is the weakest, and it gives enough to insert the sectional jimmy, which the screw handle is part of. The jimmy is then inserted in the part forced out, and the safe is then torn asunder and its contents easily appropriated. This work is accomplished without much noise. INVENT NEW DEVICES. However, these new one-piece safes have not discouraged the malefactors. They have only suggested to them the creation of special appliances which enable them, without stopping to pick the lock, to remove from the side wall of the safe a circle of the metal large enough to allow of an arm to be put inside. One of the most important of these new devices for assisting the safe-crackers in their crime is formed of an iron hoop furnished with well-tempered steel teeth, which is fixed by means of a simple pivot on the safe after a screw worm has been previously driven in. The instrument is then turned on its pivot and plows a groove in the safe wall each time it revolves.