You succeeded! Congratulations!

For future reference:

1) Find the last number using the "sticking places" test.

2) The possible first numbers are the last number and 9 other numbers, 10 numbers in all, equally spaced, 4 apart, on the lock dial. The first number and the last number can be the same.

3) The 10 possible second numbers are equally spaced, on the lock dial, half way in between the possible first numbers.

4) For each possible first number, you may safely skip the second numbers that are 6 marks and 2 marks before the first number, on the lock dial. You may also safely skip the second numbers 2 marks before and 2 marks after the third number. This leaves 64 combinations to try.

Please be careful how you use your new found knowledge. If you are a school student and demonstrate your knowledge to friends, you are likely to be the prime suspect in every locker theft in the future. Even when something hasn't been stolen, but is missing and presumed to have been stolen because the owner is "sure" he or she placed it in the locker, you will be suspected of stealing it. If you decide to show your knowledge to friends, anyway, please tell them about these web pages, so they will know that other people have the same knowledge that you have.

If you use the knowledge properly, you can find locks in dresser drawers, on second hand bicycles, and elsewhere, figure out the combinations and put the locks back in service. Furthermore, you will recognize the vulnerability of a Master Combination Lock and use it only as a light security device.

For an explanation of why the methods work, please click here:

How and Why It Works

If you have one of the "new" locks or need to open a lock from another manufacturer, click here for a general purpose technique for opening combination locks:

Opening the "New" Locks or locks from other manufacturers

The methods for finding the combination to a combination lock have been known for many years, long before these web pages were written. Here are one page which also describes the techniques:

Nathan Hillson's Page

The following page describes an automatic combination lock cracker, constructed for a computer class.

The Locracker

In addtion, there was a web site,, but the site is no longer active. The domain name is currently registered to Master Lock company.

In addition to these methods, it is possible to "cheat" and get the combination if you know the serial number of the lock. Master Lock kept records of combinations by lock serial numbers. Thieves may have access to the combinations via "leaked" codebooks. Master Lock acknowledges, on its website, that it has the combinations by serial number, and will provide the combination with proof of lock ownership:

Master Lock Web Site

Besides the purposes mentioned, this information is provided to make more people aware of the security limitations of Master Combination Locks, so they won't count on a higher level of security than what the lock provides. Hopefully, this knowledge will result in less thefts, not more, because, whenever possible,  people will not store items of value (such as wallets and purses) in lockers secured by Master combination locks, and will only store items that that thieves won't want (such as dirty gym clothes.) For our locker security precautions and advice on selecting more secure locks, please click "Locker Security Precautions." For a relevant news article about locker thefts and combo lock security, please click "News Article on Combo Lock Security."

Locker Security Precautions                          News Article on Combo Lock Security

For our pages on Master 175 and its family of thumbwheel padlocks:

Methods for Opening Four Digit Thumbwheel Combination Padlocks

We trust that you will use your new knowledge in a responsible manner.

For a humorous story about opening a combination lock, please click here.

For a description of an alarm clock locker prank, click here.

Please sign the guest book below. You may also write to me:
Archived Guestbook                  Return to home page