Find the Combination to Your Master Lock!




Introduction: Find the Combination to Your Master Lock!

Here's an experience I, and most high school students go through at some point in their life.  You wake up in the middle of the night, and remember that you need a padlock for P.E. the next day.  You quickly rummage through all the junk in your room, and find about five of them, but you have no clue what the combination is for any of them.  You look on the Master Lock website, and there's a two-month process you can go through to get the combination.  You look on youtube and all you can find is a guy with a weird equation that only narrows it down to 100 combinations, which could still take up hours of your time.  This instructable will show you how to find the combination to a master lock.  **Notice!  This is only to be used in an emergency where you need to open the lock.  You should never use it to break into someone else's gym locker.  Besides, there's nothing in there but smelly, sweaty gym clothes, and maybe a stick of deodorant.

Step 1:

Find the newest looking padlock you have.  This will work with most master locks, but probably not the really old ones.  You will need a padlock and a FLATHEAD screwdriver.

Turn the lock so the back side is facing up.  Pry up the edges around the back using the screwdriver.  It is only important for you to pry up the bottom half of the circle of edges.

Step 2:

Once you have at least the bottom half of the edge circle pried up, you should be able to slide the back panel off, so it looks like it does in the picture.

Step 3:

There should be a circular hole like in the middle of the picture where you can see the edge of a circular metal disk.  If your lock by chance does not have one, you can try another lock that might, or attempt to drill a hole.

Step 4:

Clear the lock by spinning the dial clockwise a few times.  Once it is cleared, look through the hole in the back.  Rotate the dial clockwise until you see a notch in the metal disk inside the hole, like in the picture.  Then, look at what number the arrow on the front of the lock is pointing to.  That is the first number in your combination.  Write it down.

Step 5:

Now look through the hole in the back again.  Through the notch in the metal disk, you should be able to see another metal disk.  Turn the dial counter-clockwise until you see a notch in that disk as well, that lines up with the first one you found.  Record the number on the front as your second number.

Step 6:

Again, through the two notches you lined up, you should see a third metal disk.  Turn the dial clockwise again until a notch in the third disk lines up with the other two.  Record the number on the front as the final number in the combo.  Pull on the shackle, and the lock should open right up.

Step 7:

There you have it.  Slip the back back on, pry the edges back to where they were with the screwdriver or by pushing it on a hard surface.  It may turn out a bit bumpy in the back, but it is a small price to pay to pass gym.  I have used this multiple times and it works.  DO NOT MISUSE THIS INFORMATION.  I WILL NOT ASSUME ANY RESPONSIBILITY FOR ANY STUPID WAY YOU ABUSE THIS METHOD.  If you have any questions, comments, or emotional outbursts, feel free to leave a comment, and I'll try to get back to you.

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    63 Discussions

    Remember to mark where the back and case align before taking it apart. Needed to drill the hole in my model. Used a 5/16 drill bit. Took about a minute and a half. After that, it all worked perfectly. Helped that I remembered pat of the combination, once the numbers started lining up. Sure easier than the mathematical solution.

    I remember helping my friend get his locker open with this technique, The only problem i found on the lock he had was that it had to line up with a notched lever. The holes may line up properly, but unless you line them up to allow the lever to extend further there's no way it'll budge!

    Option B. Drill a very small hole on the back at the 10:30 position 3/4 inches from the center. Then use a paperclip to decode the combination.

    Excellent instructable - I love that something quite complex can be solved so simply!

    Re The Great Screwdriver Debate - I think I just call it a screwdriver, or a normal screwdriver, or a flat screwdriver, or a plain screwdriver, or an "ouch you B*****d!" when I've stabbed my hand with it trying to use it as a pry-bar :(. I may have used the terms flat-head, flat-blade, flat ended, or whatever, but I don't remember and I don't really care. Anything else I call it pozidriv, philips, torx allen, a nut-spinner, ... whatever it happens to be. Most of the time I don't call any of them anything because I'm using it not talking about it. You use language appropriate to the situation - if it's design engineering you speak that language, if it's Instructables or similar, you speak to the masses.
    Just my 2p's worth.

    Guys, can't you just do these the old way? You just keep tugging lightly on the lock as you rotate the dial CCW, then when it pulls a bit, you reverse directions, and a third time and that's your combo.

    Perhaps they've safeguarded them on more modern locks, but I've done this on dozens of locks and it really works. No drilling no muss. It's also possible to undo a lot of these with a shim.
    Or you could just...y'know...remember your combo.

    7 replies

    Yeah, I've done a bit of reading up on this. There's a lot of methods on youtube, including ones using a pop can to make a shim, a bobby pin, and math to suss out the code. I don't have a Master Lock, but on the cheap combo lock I could find, it's very easy to feel the discs turning and locking into place. I assume it must be harder on a MasterLock, but I'm going to have to wait until I have one to try.

    Point of all this should really be that a MasterLock, or any combo lock, is not a secure way to lock anything. Use a serious key lock, or just use a twist tie.

    I've done the math one, it worked pretty well. I only had to go though about 20 combinations out of 100 to get it. Haha, twist tie.

    I tried the twist-tie security method to keep honest people honest. But it was too tempting to the dishonest people who were not smart enough to figure out how to crack a combination lock. 99 out of 100 people who want to mess with you will do it if you don't use a real lock. Only 1 out of 100 of these jerks is smart enough to learn the skills to pick a lock. Twist-ties failed me 99% of the time, a lock only failed to protect me 1% of the time.

    I'm not sure how to reply to that. I guess I've never had either method fail that I remember...? So I agree with you, I think, inasmuch as: A deterrent is only as strong as the person facing it thinks it is. A master lock is much more serious-looking than a twist-tie, but it's still easy foiled. There's better locks in the world.

    Haha, doesn't seem like the best would be a little better :P