These receptacles, which come in several different colors, are easily identified: they have two identical outlets, each with three plug-in slots.

Each outlet has an arched slot at the bottom that grounds the appliance; above that are two narrow slots— the wider one is neutral and the narrower one is hot. Check the amperage and voltage requirements of the appliance you intend to plug in to the outlet against the amperage and voltage of the outlet, which are clearly shown on the front of the outlet itself.

Some duplex receptacles allow for back wiring instead of side wiring because it is a simpler process; however, back wiring is not as secure a connection as side wiring and may not even be allowed by local codes, so check before replacing or installing a new outlet. The best option is to purchase a duplex outlet that has both types of connectors.