2-Turn the lock’s dial clockwise to zero. It is a good idea to turn it at least three rotations first, just to make sure it’s clear.
3-Apply steady tension to the shackle and turn the dial clockwise. The shackle is the u-shaped part of the lock that goes around whatever you’re locking. To apply tension you can either pull the shackle up while holding the lock, or you can pull the lock down if the shackle is locked onto something solid. Turn the dial slowly as you apply tension. If you can’t turn the dial at all, release the shackle and turn the dial clockwise just a number or two and then try it again.
4-Find the first sticking point.
As you turn the dial clockwise with tension on the shackle, you will come to a point where you can’t turn the dial anymore. Make note of where it stops. Sometimes it will stick right on the numbers, but sometimes it will be between the numbers. If so, record the number to the half (e.g. 22.5, 7.5, etc.).
While continuing to apply tension to the shackle, turn the dial as far left (counter-clockwise) as you can. Make note of where it stops. Now you have a sticking "range."
Determine the sticking point by finding the number that's in the midpoint of the sticking range. A range of 4 and 5 would have a sticking point of 4.5. A range of 22.5 and 23.5 would have a sticking point of 23.
5-Release shackle tension and turn the dial slightly past the sticking point. Turn the dial clockwise about one number from the sticking point in order to allow you to "escape" that sticking point.
6-Reapply tension to the shackle and continue turning the dial clockwise to find all the sticking points. You should find a total of twelve sticking points in one complete turn of the dial. Write them down.
7-Find the third number of the combination.
Look at your list of sticking points and eliminate all those which are not whole numbers (i.e. cross off any number that ends in .5). You should eliminate 7 of the 12 numbers with this step.
Of the remaining sticking points, choose the one with the unique digit in the "ones" position. Four of the remaining five numbers will share the same number in the "ones" place, so for example, if the numbers left on the list are 4, 14, 24, 27, and 34, the number 27 is the only one which does not have a four in the "ones" place. This is the third number of the combination.
8-Find the magic number. Divide the third number of the combination (27 in this case) by four and write down the remainder. In this case 27/4 = 6 remainder 3. Remember we are only concerned with the remainder, which will always be 0, 1, 2, or 3. Write down the magic number (3 in this example).
9-Find the possible first numbers of the combination. Add 4 to the magic number (3). Write down the result (7). Now add 4 to that and continue adding 4 to each resulting sum until you have gone completely around the dial once. Write down each of these numbers. Thus, for the example above the numbers would be 3, 7, 11, 15, 19, 23, 27, 31, 35, and 39. One of these numbers is the first number of the combination.
10-Find the possible second numbers in the combination. If your magic number is 0 or 1 then add 2 to it, otherwise subtract 2. Since our example magic number is 3, we subtract 2 and get 1. Write down the answer and add 4 to it. Now add 4 to each resulting sum until you have gone completely around the dial once. Thus, in the example, the numbers would be 1, 5, 9, 13, 17, 21, 25, 29, 33, and 37. One of these numbers is the second number in the combination.
11-Cross out the numbers (the possible 2ND numbers) Plus or Minus 2 [25 & 29] from the third number of the combination.
12-Figure out the correct combination by trial and error. You now know all the possible first numbers [3, 7, 11, 15, 19, 23, 27, 31, 35, 39], all the possible second numbers [1, 5, 9, 13, 17, 21, 25, 29, 33, 37], and the third number . You’ve just narrowed down 64,000 combinations to only 80. Now try each combination until you find the correct one. If you’re lucky, you may need to try only a few but then again, you may need to try all 80.
If you’re in a hurry, you don’t need to calculate the possible first and second numbers yourself. Once you’ve figured out the third number, you can save time by using a special computer application to determine all the possible combinations.