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.

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.

Step 1: 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.

<p>Used this to reset my Pure Gym branded padlock, which had been left open and forgotten. Cheers!</p>
Mate me too I opened my gym bag after 2 years only to realise I forgot the code to the PureGym padlock! This Instructable saved me 4 quid haha.
<p>Well then how about this situation...</p><p>I have a 1535dwd from master. It's a 4 letter combination. It's already opened, but the combination to close it is needed. How do you find what the combination is?</p>
Holy crap!!! I really didnt think this would work at all but good Lord it did!! My jaw dropped as soon as it popped open. Hats off to the person who figured this out!! Wow!!
<p>No way. you need a shim. Like a .005 feeler gauge. You insert the gauge between the housing and the dial. All #'s will allow the gauge to go in a set distance. Except one. The gauge will go in a couple mm more. Do that with all 4 dials. Say the #'s are 4789. rotate each dial togeather,trying to open at each one. i.e. 4789,5890,6901,7012,etc. pulling on the hasp is useless. I use a small tape measure end about 2: long that is perfect. Has the marks at each 1/16</p>
<p>That is nuts how easy that is. That's like stupid easy. <br><br>Had a lock sitting around with an unknown combo, within seconds it was open. Thankfully I'm an honest man.</p>
Great I did it thanks :)
Damn ! this trick worked and saved my a** !!<br><br>thank you very much for sharing it !
ThaNks this the best
Thank you. I've had this kind of lock sitting around being neglected for about a year. This is so helpful
<br> Don't use this type of lock with anything valuable, they are way to easy to open.<br> <br> 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.<br>
Thanks <br>this was my brothers lock that he forgot the combo too but i opened it!!

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