Wipe the area around the crack with a damp washcloth and allow it to air dry.
Place a dropcloth on the floor, pushing it as close to the baseboard as possible to protect the floor from spills.
Run a utility knife along the inside of the crack in the sheetrock to clean out any loose debris. Sand the surface of the crack using 220-grit sandpaper until there are no pieces of sheetrock sticking out from the surface of the wall.
Cut a piece of stress-crack tape 2 inches longer than the crack. Remove the adhesive backing and smooth the tape over the crack, extending it 1 inch past either end of the crack. Push out any air bubbles and make sure the tape is flush against the wall by running a putty knife over it.
Apply a layer of joint compound over the tape and around the edges where the tape meets the wall, using a putty knife. Keep the layer of joint compound thin, but still thick enough to cover the mesh of the tape. Let the compound dry according to the manufacturer’s label.
Smooth out the joint compound with 220-grit sandpaper until it is even with the rest of the wall. Wipe the wall clean with a tack cloth or damp washcloth. Repaint with the same color and sheen used on the wall.