How The Method Works
How we find the last number:

You will note that the front cam is attached directly to the turning knob of the lock. When the shackle is pulled up, the latch assembly pivots toward the cams. When the deep notch on the first cam and the notches of the other two cams are lined up under the pawl and the shackle is pulled, the latch assembly pivots far enough to allow the shackle to be pulled out, unlocking the lock. When the notches on the middle and back cams are not lined up, but the front cam deep notch is lined up, the pawl pushes against the middle and back cams. If the dial is turned while the shackle is pulled, the dial will stop when one side of the notch hits the pawl. The knob can be turned back and forth. The knob stops when either side of the notch hits the pawl.

If there were only one notch on the first cam, the deep notch, as there was in older Master locks, the dial would be at the correct last number. The eleven shallow notches were added and help to conceal the last number. The shallow notches are usually deep enough that, when a shallow notch is under the pawl, the pawl will be held back by the other two cams. As the dial is turned back and forth, the sides on the notch hit the pawl, and the dial stops.

To effectively hide the deep notch (last number of the combination,) the shallow notches should be indistinguishable from the deep notch. However, Master left some clues to help us find the deep notch. The deep notch should be centered very close to a number, the last number of the combination, so notches centered between numbers are not valid. (Actually, the deep notch center has been found slightly to the right of the correct last number on many Master locks.) At least four of the shallow notches are between numbers. For some unknown reason, Master placed four of the remaining shallow notches, that are lined up with numbers, fairly precisely ninety degrees apart. Part of the procedure locates those four notches and eliminates them as possible last numbers. Also, on some locks, Master made some shallow notches narrower than the deep notch. The narrower notches can be eliminated. The valid notch must be wide enough to allow some sloppiness in dialing the combination. The narrow notches do not have to be wide to allow for sloppiness, but should be the same width to disguise them from the valid deep notch.

On the older Master locks, we go to extra effort to locate the correct last number. We do that because the first, second and third numbers are related. After we have found the correct last number, there are only 64 combinations to try. On the new Master locks and on locks from other manufacturers, we do not know the relationship between the first, second and third numbers. We don't even know if they are related. However, once we have dialed the correct first and second numbers, the deep notches on the middle and back cams will line up under the pawl. If we turn the dial to a fake sticking place and pull the shackle, the only cam holding back the pawl will be the front cam. If we turn the dial while pulling the shackle, the pawl will scrape against the bottom surface on the fake notch, creating extra friction and making the dial harder to turn. When we notice this extra friction, we will know we have the correct first two numbers and it is a simple matter to turn the dial to each of the sticking places, one at a time, and pull the shackle. The lock will open at the correct last number.

The shallow notches, on some locks, may not be deeper than the surface of the other two cams. Then, the pawl will rub against the bottoms of those shallow notches when the shackle is pulled and dial turned. This rubbing makes the dial slightly harder to turn, and can be used to detect that the notch is shallow. On the "new" Master locks, we can't use these very shallow sticking places to test whether we have dialed the first and second numbers correctly. However, we can find these sticking places ahead of time, and avoid using them. If all 11 fake sticking places are this way, we don't mind. We'll use the 12th sticking place, the correct last number, to check whether we have the first and second numbers dialed correctly!

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