Steps required to repair a loose door knob include removing the door knob, removing the base, locating and tightening screws, and securing the door knob to the door. Door knobs either have exposed set-screws or hidden screws. Exposed door knob screws are easy to see and are usually removed with an Allen key or screwdriver. Door knobs with hidden screws have a detent access hole and the best tool for removing these screws is a flathead screwdriver.
After loosening the screw using a screwdriver, remove the door knob handle and set it aside. If working with a door knob that has a hidden screw, find the tiny spring-activated pin sticking out of the dent access hole. Using a flathead screwdriver, gently press down on the pin to release the knob. Next, use a flathead screwdriver to slowly pry away the ring section of the base without damaging its backing plate. The set-screws are visible at this point; they run through the inside backing.
To tighten the set screws, hold the outside backing plate steady with one hand while using a screwdriver to tighten each screw. Replace the ring back section of the backing plate. Position the knob back onto the spindle shaft and turn until the holes line up with the detent and the knob clicks into place.