I used to cut a piece of plywood slightly narrower than the hole; then cut the ply wood, or solid wood works too, to a length longer than the hole, put the ply behind the sheetrock, put a screw partway in the wood where the missing rock hole is, slide this behind the sheetrock, hold it by the screw in the hole tightly then screw through the surrounding rock board with enough screws to hold it all in place, it will be stronger than the original wallboard in that area. It works like a charm. And for homeowners who have a heavy picture to hang, they now have a place to hang a heavy picture as you now have a section of drywall with a backing of plywood.