Outlets
Outlets, also known as receptacles, are the places where you plug in your lamps, computers, toaster ovens, and blow dryers.

Some include a half-round hole for the grounding plug on a cord. Older houses may not have outlets with grounding holes, in which case you probably have two-prong adapters to ground your appliances and lighting. If you have to replace an outlet, install a grounding box unless the system isn't grounded with a grounding wire or metal conduit.

How do you know if the system has a grounding wire? First turn off the power. Check an outlet with a circuit tester to make sure it's off, and remove it from the wall. It should have three different-colored terminal screws: brass screws for black (hot) wires, silver screws for white (neutral) wires, and a green screw for the ground wire. The green terminal screw should be connected either to a bare wire or to a metal electrical box. If it isn't, consult an electrician to find out whether your system is properly grounded.

Outlets for 240-volt appliances that draw a lot of current (such as dryers, ranges, and air conditioners) have different configurations. Never force a plug into a outlet that doesn't accommodate it. Always replace old outlets with new ones that have the same amperage and voltage.