In the average home, most switches are of the single-pole type—an on-off toggle controls a light or outlet from a single location. The basic structure of single-pole switches is this: There are two same-colored terminals, usually brass or silver for wire connections, and it is obvious which side is up.

Some have terminals for backwiring, and all are wired into hot wires only. You may use copper or aluminum wire for switches marked “AL-CU,” but unmarked receptacles, and those with the “AL” symbol slashed through, can only use copper wire.

While it used to be that traditional 120-volt switches had no grounding wires (their plastic toggles were considered shockproof), many of the switches now have grounding terminals, and installing them is similar to that of a grounded receptacle. Here is how to install a single-pole light switch:

1) Strip the outer coating of insulation from the wires.

2) Join the white neutral wires, if there are any, and cap them with a wire nut.

3) Join the grounding wires with either a compression sleeve or wire nut. If you are using a metal box, include a grounding jumper from the box.

4) Connect the hot wires to the switch’s screw terminals. While it does not matter which wire goes to which terminal, secure the grounding jumper to the green grounding terminal.

5) Mount the switch. First, fold the wires behind the switch and carefully push the switch into the box. Next, align the switch vertically by adjusting the screws in the mounting slots. Also make sure the switch is flush with the wall.  If it isn’t, shim it out using the break-off portions of the switch’s plaster ears or use special washers sold for shimming purposes. Screw the switch to the box.

6) Screw the faceplate of your choice to the switch, using the screws included with the faceplate.

In addition to wiring a switch of the single-pole type, you can wire three-way switches that allow you to turn the light on and off at two different locations, such as at either end of a hallway or stairwell. It is also possible to wire a four-way switch that allows you to control a light from three locations. Just remember the cardinal rule when working with electricity: Make sure the power is turned off to the area you are working on.