Creep is the trigger sear moving thru the hammer sear. On the old rugers this is a direct impingment system. Limiting the creep is done by limiting the sear engagement. Material is either stoned from the outer edge of the hammer sear so that there is simply less notch for the trigger sear to move thru or a pin or other device is used to keep the trigger sear from fully engaging the hammer sear notch. This also limits the sear travel.. and thus the creep. Either is a fairly touchy operation and if the sear angles are changed or the edges rounded off a dangerous situation can develope. I usually reccomend a good gunsmith unless your a fairly accomplished ameture gunsmith..