Things You'll Need
12/2 or 14/2 electrical cable
Electrical wall receptacles are wired together in a circuit from one to the next, and to the next, until the circuit reaches the last receptacle. The last receptacle is known as the end-of-run receptacle, where the other receptacles are known as middle-of-run receptacles. Wiring two receptacles back to back is when there is a receptacle on each side of an interior wall, with one receptacle being wired and getting its power from the receptacle on the other side. Back-to-back receptacles can be installed with either middle or end-of-run receptacles.
Turn off the power to the receptacle circuit being worked on at the corresponding circuit breaker in the breaker box. Plug in a portable electrical appliance (such as a lamp) into each receptacle in the circuit to make sure the power is off.
Unscrew and remove the faceplate on the receptacle that the new receptacle on the other side of the wall will be attached to. Also remove the screws holding the receptacle to the wall box, and carefully pull out the receptacle.
Feed a length of 12/2 or 14/2 (with ground) electrical cable from the receptacle's wall box through the interior wall cavity and into the new receptacle's wall box on the other side of the wall. Make sure there is 8 inches of cable in each box before cutting the cable from its roll with a wire cutter.
Strip back the outer sheathing on the new cable within 1 inch of where it enters into the each box (use a utility knife). Cut off 1/2 inch of plastic coating from the ends of all black and white wires, using wire strippers. Bend the ends of all wires into hook shapes, using long-nosed pliers.
Attach the black wire in the new box to a brass terminal on a new receptacle, and tighten the screw to the wire. Attach the white wire to a silver terminal on the new receptacle and tighten the screw. Attach the bare ground wire to the ground terminal on the new receptacle, and tighten the screw. Push the wires and receptacle into the box, securing the receptacle to the box with the two screws. Attach the faceplate to the front of the receptacle with the screw.
Attach the black wire coming out of the existing receptacle box to one of the brass terminals on the receptacle and tighten the screw. Some receptacles have an inlet hole next to each black and white terminal; if that is the case, simply push the black wire end into a hole next to one of the brass terminals. Attach the white wire to one of the silver terminals (or inlet hole). Tighten the screw. Attach the bare ground wire to the ground terminal and tighten the screw.
Push the wires and receptacle into the box. Secure the receptacle to the box with the two screws, and fit the faceplate to the front of the receptacle with the screw. Turn on the power at the breaker box.
Use the same gauge wire (12/2 or 14/2) as the existing wire in the receptacle circuit. If in doubt, call the local city building department for the correct gauge wire in your area.
Make doubly sure that the power is off before working on the receptacle circuit.