Instructables
Picture of How to Reclaim A Master Lock 4 No. Combination
Okay, so, you have a somewhat expensive Masterlock with a 4 number turning combination.  Unfortunately, you have lost or forgotten the combination that opens this particular Masterlock.  Bummer. 

With four sets of digits, opening this lock has approximately 10,000 possible combinations.  Actually, it has EXACTLY 10,000 possible combinations.
Bummer.

Fortunately, these locks have a very simple, intuitive lock mechanism.  The next step will briefly describe the mechanism, and subsequent steps will show you how to actually reclaim the combination, meanwhile opening the lock as well.

Disclaimer:  Don't steal people's things.

 
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Step 1: Inner Mechanical Workings (FYI)

Picture of Inner Mechanical Workings (FYI)
First off, if you want a detailed explanation of combination locks, pop over to Wikipedia

Imagine a Master combination lock as simply a a number of discs (or rotating dials) with notches in their inner circumference.  These notches correspond to a particular number on the outside of the disc (the part we use to unlock it).  When the correct number sequence is inputed, the notches line up, and the bolt is released.

The most important things to know are (1) all 4 numbers must be correct to release the bolt (2) as we can't see the notches, we have to rely on touch to feel when a notch is engaged or not, (3) in order to feel when a notch is engaged, we need to provide upward pressure to the bolt, and (4) in order to feel each number out correctly, we must start from the bottom up as this will allow us to know when each subsequent notch (up the lock towards the bolt) are engaged.

Enough of this.  Lets pop a lock.

Lowriderpr2 years ago
Great I did it thanks :)
manutea2 years ago
Damn ! this trick worked and saved my a** !!

thank you very much for sharing it !
sbeltran32 years ago
ThaNks this the best
St Jimmy4 years ago
Thank you. I've had this kind of lock sitting around being neglected for about a year. This is so helpful
Dr Qui St Jimmy3 years ago

Don't use this type of lock with anything valuable, they are way to easy to open.

When I worked in the hardware store we used to have one of these locks that we played a game with, see who could open a the lock the quickest without knowing the combination, we could open the lock in under 30 seconds before to long.
tranoxx3 years ago
Thanks
this was my brothers lock that he forgot the combo too but i opened it!!
KnexFreek4 years ago
 THIS IS AWESOME THANKYOU!!!!!