If the drywall has crumbled under stairway handrail brackets, take them off and cut out the damaged drywall using a hole saw slightly smaller than the brackets' bases. Use the same hole saw to cut plugs out of ½-inch plywood; put one plug in each hole. Reattach the brackets through the plugs into the studs. The plywood provides a much firmer foundation than drywall.
— Jiri Klinovsky, East Moriches, N.Y.