Faster Lock Combination

Tools/Skills: Designing & documenting a repeatable solution to a problem; How to crack a rotary lock in the real world

SYNOPSIS

Find the 9 possible combinations to a rotary lock. Use trial and error to find the correct combination.

Following the instructions as laid out in the video, I was able to find the correct combination to the rotary lock. I've documented all steps below, so that if anyone wanted to repeat my steps they could.

SOLUTION & PROCESS

*Watched How-To Video

1. Identify sticky number and the guess numbers:

   STICKY #: 29

   • The most obviously sticky number

   GUESS #s: 8 , 9

   • Check every interval between 0 and 11.

   • Start at 0, apply full pressure, try to rotate the lock, does it wiggle between whole numbers or half numbers? If whole → skip it. If half → it’s a guess number.

   • Move the lock to 1 and repeat.

   • Repeat for numbers 2 through 11 until both guess numbers are found.

2. Find 1st Number (34)

   Sticky Number + 5

   29 + 5 = 34

3. Find 3rd Number (18)

   • Remainder when you do: (1st number)/4

   • 34/4 → remainder of 2

   • Take your two guess numbers and add 10 to each three times

     8 18 28 38

     9 19 29 39

   • Divide each of the numbers in step B by 4. Note the two numbers that have the same remainder as your 1st number: (In this case, a remainder of 2)

     18, 38

   • Decide between the two numbers.

     • Go to the first number (18), apply full pressure, try to wiggle it.

     • Do the same with the second number (38).

     • Which one wiggles more (or is looser)? That’s your 3rd number: 18

4. Narrow down 2nd Number

   1. Remainder + 2, add 8 four times

      4, 12, 20, 28, 36

      Remainder + 6, add 8 four times

      8, 16, 24, 32, 40→0

   2. Remove any options that are within two digits of your 2nd number

      • Remove 20 and 16

   3. Final options:

      4 12 20 28 36

      8 16 24 32 0

5. Test all options until the lock opens

   34 → 4 → 18

   34 → 8 → 18

   34 → 12 → 18

   34 → 24 → 18

   34 → 28 → 18

   34 → 32 → 18

   34 → 36 → 18

   34 → 0 → 18

6. I got quite lucky on mine. My first attempt was correct:

   34 → 4 → 18