Is SU24 only for removing security checks?

We have R3 4.7 - I have been doing security for a number of years but just recently went to the ADM950 class, there the teacher said you could change the check indicators to do MORE checking than what the SAP delivered standard provides and those checks will be done in SAP programs. Sounded pretty far out to me but if it can do this please tell me how to change a check indicator from check to check-maintain. Thanks Alot.

Jim Wells