Often it seems there are not enough electrical outlets in a room to power the myriad of electrical devices of modern society. Plug adapters can be plugged into an outlet to increase the number of devices which can be plugged into an outlet, but adding another outlet is a better solution. An existing electrical outlet (plug) can be used to feed electricity to an additional outlet.
How to Splice Into an Existing Electical Outlet to Power a Second Outlet
Turn off electrical power at the breaker panel for the existing outlet. Verify the plug is not hot by plugging a device into the plug. If the device does not turn on, the power is off.
Remove the cover plate on the existing plug with a screwdriver. Back out the screws holding the plug into the plug box. There will be one at the top of the plug and another at the bottom. Pull the plug out of the box, being careful not to pull the existing wiring off the plug.
Cut the new wires--black, white and green--to the desired length and strip approximately a half-inch of the insulation off each end of the wire. Locate the white and black, or red, wires on the existing plug. Attach the new black wire to the same terminal as the black wire on the existing plug using the proper screwdriver; loosen the terminal screw, slide the new wire under it, along with the old wire, and tighten. Attach the new white wire to the same terminal as the white wire on the existing plug. Attach the new green to the same terminal as the green or bare wire on the existing plug.
Hold the new outlet so it is oriented the same as the existing plug. Attach the new wires to the new plug terminals to match the wiring of the exiting plug; white and black wires should go to the same side of the plug. Green wire should go to the ground terminal on the new plug. The new plug will now receive power from the existing outlet.