This article is from the Locksmithing FAQ, by Joe "Spike" Ilacqua spike@indra.com and Henry Schaffer hes@ncsu.edu, major data collection effort by Scott Anguish sanguish@digifix.com with numerous contributions by others.
The better safe locks can be changed to a new combination.
This involves insertion of a "change key" into the back of the
combination lock, and dialling the new combination. Usually the new
combination is dialled using a "change index" rather than the usual
"opening index" (usually located at 12 o'clock.) There are restrictions
on choice of the numbers - so be sure to find out the details before
doing this yourself. Carefully review the instruction sheet for the lock
(example)
before doing this.
WARNING: It is hard to open a safe which has been set to an unknown
combination or one which doesn't work. So be sure to exercise the new
combination several times with the door open before closing the door and
locking the safe.
 
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