Everything I Know About Masterlock Combination Locks By: MMDeveloper;
Last Updated: 2017/07/24

Prologue

There are probably some of the more prevelant combination locks out there. They are very popular with locker type spaces. Luckily, picking these things is pretty easy, thanks to math.

Picking

Narrow Results
Combinations

Instructions

  1. Reset dial and rest on 0.
  2. Pull up on the shackle with one finger and rotate the dial toward the number 5 until you get stuck inside of a groove.
  3. Wiggle the dial back and forth. If the leftmost and rightmost boundaries of the groove end on whole numbers (i.e. not between numbers), skip this groove and repeat. If you exceed the number 11, you've missed it, restart.
  4. Once you find the groove whose bounds are not on a whole number, note the whole number that the dial skips over when bouncing back and forth between groove sides. Put this number in the 'First Number' box.
  5. Repeat from Step 2 to find the second whole number. Put this number in the 'Second Number' box.
  6. Release shackle and reset dial, setting it back to 0.
  7. Pull up on shackle slightly. Not so hard that it binds in grooves, but just enough that while spinning dial, the dial will snag on one number each rotation. It will be the same number each time. You may need to rotate the dial several times until you find the right amount of tension on the shackle.
  8. Once you adjust the shackle tension to the point you are only snagging on one number each rotation, put that number in the 'Snag' box.
  9. Click the 'Find Combinations' button.
  10. Take note of the two possible 3rd numbers and reset the dial.
  11. Turn the dial to the first of the two 'third' numbers.
  12. Pull up on the shackle as in Step 1 and rotate the dial back and forth. Take note of how wide the groove is, including partial numbers (i.e. 4.2, 12.5)
  13. Reset the dial and repeat for the second 'third' number.
  14. Determine which of the 3rd number grooves was the widest and click that button to set as the 3rd number.
  15. You are now presented with possible combinations with the first number, 8 possible second numbers, and the last number. Cycle through them until the lock opens (R1, secondNumber, R1).
  16. You can click on each 'possible combination' to change its color so you can keep track of ones you have already tried.
  17. If the lock did not open, you did not locate one or more of the numbers from previous steps properly.
  18. For more information:

This alternative method illustrated by the Reddit user /u/Speculator