Frequently Asked Questions
Question: How do I change the combination on a "Set-Your-Own" combination lock model #643D?
Here are the instructions for changing the combination on your model 643D lock. This lock is preset at the factory to operate at 0-0-0-0.

1. With dials at 0-0-0-0, pull out the shackle.
2. Turn shackle 90 degree (1/4 turn) so notch on shackle is aligned with notch in lock body.
3. Press and hold the shackle down.
4. Set the dials to your own combination by lining up middle of numbers with red stripe.
5. Lift and return the shackle to closed position.
6. Scramble the dials to lock.

Note: Be sure to record your NEW combination as you are the only one that knows it!

Store your combination at - a FREE service from Master Lock! The Master Lock Vault provides a safe & convenient place to store all of your confidential data for quick & easy access from your PC, iPhone, or any other mobile devices!

Note: The lock may only be reset when it is in the open position. If you do not recall the combination the lock is set to, you will not be able to reset the combination.