The Sargent & Greenleaf (S&G) Group 2 combination lock is a heavy-duty safe lock with more than 1 million possible combinations. The company uses it to secure a variety of safes. Changing the lock combination regularly helps prevent against theft and tampering. The lock has a high level of security, and although the method for changing the combination is bit involved, it is not too difficult to follow.
Enter the active combination and open the door.
Leave the door open, but relock the lock by spinning all three dials at least a couple notches.
Enter the combination again, using the "changing index" guide located at the 11 o'clock position, rather than the regular guide marker at the 12 o’clock position.
Insert the lock change key into the side of the lock panel. This key comes with the lock and looks somewhat like an Allen wrench.
Rotate the key 90 degrees counter-clockwise.
Spin the wheel four full turns counter-clockwise, then end on the first number of a new combination. Again, align the numbers with the "changing index" marker.
Spin the wheel three full turns clockwise, then end on the second number of the new combination.
Spin the wheel two full turns counter-clockwise, then end on the third (and final) number of the new combination.
Spin the wheel clockwise exactly 10 digits.
Rotate the change key 90 degrees clockwise to lock in the combination.
Test out the combination several times before closing the door.