Why Your Master Lock Sucks

How to Shim a Lock

So What's the Deal?

With over 64,000 possible combinations you are probably pretty comfortable with your combo lock investment. Hell, why wouldn’t you be, with that many different variations an intruder would average 3,733 hours and 20 minutes trying to crack your combo. So unless you leave your locked goods unattended for 156 days and you have an extraordinarily desperate thief that can manage trying at least half of all these different combinations continuously without sleep you should be safe right?

Of course! That is if you are willing to bet that your intruder is:
1) Too lazy to look up one of the numerous YouTube tutorials on bypassing combo locks.
2) Too lazy to YouTube “cracking” a combo lock
3) Too persistent to just hit it with a hammer

Oh snap! You have a KEY LOCK? Congratulations, +1 points to your security! Now your shady guest requires an additional five minutes of research and 20 minutes of work to manufacture a crude pick set. Yes, crude will do because your mass-produced Master Lock has a primitive design that requires nothing more than caveman-like tools to defeat.

Are you still confident with your trusty locks?

What Does it Mean to Bypass a Lock?

Bypassing is a means of opening or defeating a lock without knowing the combination or having the appropriate key. It’s like getting access without having a clue what the secret password is.

Bypassing is a technique commonly used by hackers as well. Remember Windows XP (the version before Microsoft randomly loaded software into a shotgun and blasted us with three ridiculous “new” operating systems.) A hacker could bypass the login screen by simply booting the computer in “safe mode”, going into the admin settings and turning off the username / password then restarting the computer.

So How Do You Bypass a Combo Lock?

The answer is a soda can. Or more precisely, a 2x2 inch square of tin (commonly found on soda cans) cut into a pointy triangle thingy with a folded edge. This pointy tin thingy is then slipped into the hooky part of the lock-ma-jig so that it doesn’t catch on the…catcher…inside the lock. This process is also called shimming and the tin thingies are more correctly referred to as “shims”.

Or you could just accept that it is magic.

For best results, empty the soda can before cutting.

After a little bit of practice (it does take a little bit of finesse), it is possible to consistently bypass combo locks in just a few seconds. If you are naturally clumsy or have gorilla hands with sausage fingers don’t expect to become a ninja with shimming.

The main focus should be on getting the point of the shim located directly over the notch in the lock. It doesn’t take much force to shim a lock; try moving the locking bar up and down with the shim to get it in place. Occasionally, it does work to rapidly shake it up and down hoping that it catches over the notch opening the lock.

Shimming is the fastest way (without destructive force) to defeat a lock, however, wouldn’t it be useful to know the combination, especially if you plan on using the lock again in the future?

How to Crack a Combo Lock

We already discussed the primitive design of Master Locks: try pulling down on your combo lock and wiggling the dial back and forth. Notice there’s a good deal of play with the dial. (Ever wonder why you don’t have to get your combo exactly right?)

When you do this wiggle check, notice the dial goes between either two half numbers or two whole numbers; meaning the average number in that “wiggle check” will either be a whole number or a half number. If you were to start at “0” and continue the wiggle checks all the way through all the numbers you will find that there are only five whole numbers and the rest will be half numbers. You will notice four of these whole numbers end in the same last number and one of the whole numbers is completely different. This is the last number in the combination.

Example: After doing the wiggle check you have the whole numbers:
4, 14, 24, 25, 34

Because 25 is the only number not ending in “4” it is the last number in your combination. Now you know your combo is this: XX-XX-25

The next step is to take the number 25 and divide by four and keep just the remainder.
25/4 = 4 Remainder 1

Your 1st number in the combination is going to be 4x+1 or 1+ multiples of 4. For example:
1, 5, 9, 13, 17, 21, 25, 29, 33, 37

I could explain this next part and confuse the hell out of you but I’d rather just give you the answer.

If the starting remainder was:

  • 1 then your possible second number combos start at 3
  • 2 then your possible second number combos start at 0
  • 3 then your possible second number combos start at 1
  • 0 (meaning there was no remainder) then your possible second number combos start at 2

So for my example scenario we would have “3” and adding multiples of “4” our possible second number combos will be:
3, 7, 11, 15, 19, 23, 27, 31, 35, 39

Now it’s just a process of elimination. With less than 100 possible combinations now it will only take at most 10 minutes to figure out the lock’s combination.

*Note, it is very important to get the correct last number in the combo, otherwise you will waste time and get very frustrated trying a bunch of invalid combos.*

This method works best on newer locks that are not “gummy” or sticky. Some older, more abused combo locks may be much more difficult to work with.

Why Share this Information?

So you’re not ignorant. If someone wants to steal from you, they will have planned a way and most likely will not waste time trying not to harm your lock. More realistically, this information will assist you in remembering old combos (just writing down the possible combos is usually all it takes to remember) or in an emergency, shimming into a closet or trunk if you are short on time.

Do yourself a favor and spend the extra couple dollars on a beefier, higher quality lock. It is MUCH more difficult to pick or bypass a lock that has higher quality manufacturing.

Also, don’t forget to share this with your friends so they know as well!

How to Crack Combination Lock Combo

Sesamee K436 4 Dial Bottom Resettable Combination Brass Padlock with 1-Inch Hardened Steel Shackle and 10,000 Potential Combinations
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(price as of May 12, 2016)
Having a resetting combination padlock is much harder to bypass and impossible to crack or pick.