To repair large holes after removing switches, receptacles or boxes, cut a thin piece of wood 2 inches larger than the hole. Cut a piece of hardware cloth 1 inch bigger than the hole in all directions. Apply fast-drying construction adhesive to the center of the wood and affix the hardware cloth to the wood. Allow the adhesive to dry for five minutes.
Thread a length of string through the hardware cloth and around the back of the wood so that you hold both ends of the string in your hand. Apply construction adhesive to each end of the wood and around the edges of the hardware cloth. Insert the wood and hardware cloth into the hole with the adhesive facing you. Position the wood in the center of the hole. Draw the string toward you so the wood and cloth adheres to the inside of the wall. Hold it in place until the adhesive sets, generally less than five minutes.
Apply a layer of drywall compound with a putty knife over the hardware cloth and wood while keeping tension on the string. Do not cover the string; leave a 1/4 inch gap around it. Allow the drywall compound to set for one hour.
Cut the string with a utility knife and fill in the hole with drywall compound. Let the drywall compound dry completely, typically two to three hours, and sand smooth with 120-grit sandpaper.
To repair small holes drilled when fishing for wires, sand the surface of the hole with 120-grit sandpaper to make it smooth.
Press drywall compound into the hole with a putty knife. Build it up so it sits just above the existing drywall surface.
Allow the drywall compound to dry completely, usually two to three hours.
Sand the repair smooth with 120-grit sandpaper.
To repair overcuts on receptacles, light switches and boxes, apply drywall compound to the void space between the receptacle, switch or box. Press it in to coat the edges of the drywall and outside edges of the electrical box. Remove drywall compound from the inside edges of the utility box with a putty knife.
Place drywall tape over the wet drywall compound, up to the edge of the electrical box and smooth it out with a flexible putty knife. Apply a layer of drywall compound over the tape. Allow the drywall compound to dry for one to two hours.
Apply another layer of drywall compound over the dry compound and allow it to set for one to two hours. Apply a third layer and allow it to dry. Keep the layers thin so they adhere, set and dry properly.
Sand the repair with 120-grit sandpaper so it sits flush with the existing wall.