You might know receptacles more commonly as outlets--the place where you plug in your lamps, computers, toaster ovens, and blow dryers.

Some include a half-round hole--this is for the grounding plug on a cord. Older houses may not have receptacles with grounding holes, in which case you probably have two-prong adapters to ground your appliances and lighting.

If you have to replace a receptacle, 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 at the main circuit box.

Check a receptacle 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.

Receptacles for 240-volt appliances such as dryers, ranges, and air conditioners that draw a lot of current have different configurations--never force a plug into a receptacle that doesn't accommodate it.

Always replace receptacles with outlets that have the same ampere flow and voltage; amps and voltages vary.