Steps:
1. Put on a dust mask and safety glasses. Use the pointed end of your basic can opener to widen the crack and clear away as much debris as possible (figure A). Clear away debris by vacuuming the crack.2. Pack the crack with spackling compound using the putty knife (figure B). Smooth out excess spackling with your fingers.
3. Cut strips of drywall tape and press on the wall, covering the crack. Spread a thin, even layer of drywall mud over the tape using the wide putty knife (figure C). Wipe the putty knife regular with a warm, damp cloth to clean it and help prevent lumps.
4. Sand down the rough edges using a piece of sanding mesh, a screen-like material that resists clogs. Wet sand and area with a damp sponge.
5. Dip the damp sponge in the drywall mud and dab it over the area to create texture (figure D). Knock the sharp edges off by very lightly wiping over the area with the wide putty knife.
6. Once everything is dry paint the area to match using a sponge paintbrush.