There are three types of residential electrical light switches. The first kind is a single pole light switch. The second is a 3-way switch that controls a light or fixture from two locations only. The third type is a 4-way switch that controls a light or fixture from three or more locations.

The quickest wiring method for 3-way switches is to place the light or fixture in the middle of the two switches. You’ll need to look at the wiring diagram closely to understand how it is done. The electrical cable should be 12-2 electrical wire up to the first switch, then use 12-3 electrical wire to the light and then to the second switch.

The 12-3 cable has a third wire called a traveler (usually red), which is used for 3-way switches. At the first switch, the 12-2 wire from the house circuit run enters through the bottom of the switch box and the hot (black) wire connects to the bottom right terminal on the light switch.

The 12-3 cable enters through the top hole of the switch box. The traveler (red) wire connects to top left screw or terminal on the light switch. The black (hot) wire connects to the top right screw or terminal on the light switch.

The 12-3 neutral (white) wire connects to the 12-2 neutral wire with wire nuts and the copper ground wires are connected together with wire nuts in the same fashion. At the light fixture box, there will be two ends of 12-3 electrical cables hanging out. One end comes from the first light switch and the other cable comes from the second light switch.

Next, connect the copper ground wires together with a wire nut to get them out of the way, and then connect the two red traveler wires together with a wire nut.

Now, find the black wire that comes from the first switch box and the white wire that comes in from the second box and connect them together with wire nuts. Now, here’s a really important step. You will need to mark each end of the white wire by wrapping it with black electrical tape. This means the wire is designated as a hot wire. This is a code requirement for using white wires for hot lines! It is a common practice for 3 and 4-way light switches.

Now, over to the second switch, you’ll connect the red traveler wire to the top left terminal or screw on the light switch. The white wire marked as a black hot line with tape, connects to the upper right terminal on the light switch. The black wire will connect to the lower right terminal or screw on the light switch. The copper ground wire connects to the box if it's a metal box or the green grounding screw on the switch if the box is a plastic box.

The light or fixture box should now have a black wire and a white wire sticking out so you can connect the light or fixture.

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