Before you begin, shut off power to the circuit. Use a voltage tester to check that the power is off. Mark the area where you plan to place the wall sconce. To cut wall holes for the sconce boxes and light switch, use a utility knife to trace the outline and cut the hole with a drywall saw. Run cable from the power source to the switch, then to the sconces.

Clamp cable to the wall box, tugging gently to make sure the clamp is tight. To install the box, push it into the hole in the wall, enlarging the hole with a utility knife if needed. Tighten the screws until the box is firmly attached. Most wall sconces come with all the necessary hardware for mounting, which is usually a strap with a center stud. The strap also helps carry heat away from the fixture.

To wire a sconce, splice the white fixture lead to the white wire and the black lead to the black wire. Connect the grounds. If desired, you can test the power at this point to make sure the light is functional. Remember to turn the power off again before completing installation. 

Slip the wall-mount light fixture over the center stud and start to tighten the nut. Stand back and check that the base is plumb, adjusting as needed. Once level, tighten the base.

Install the lightbulb, making sure it does not exceed the manufacturer's recommended wattage. Clip the lens into place. Wire the switch.

Editor's Tip: If you'd prefer to mount lights on a mirror, you have two options. To install a bathroom strip light, center the box over the mirror or medicine cabinet. Attach the fixture over the box, wire the fixture, and attach the cover. To install a light fixture directly onto a mirror, have a glass supplier cut three holes to match the fixture: a large hole for the electrical box and two smaller holes for mounting screws. Wire the fixture. Apply a thin bead of clear silicone caulk to its back to act as an adhesive. Attach with mounting screws but don't overtighten them—you might break the mirror.