Common Methods for Wiring 3-way
and 4-way Switches
Details:
Below are common methods of wiring up three-way switches that were taught to me by the master electrician I worked for many years ago (late 80s/early 90s).

The graphics and images were created about 6 years ago.

The page was re-vamped in 2006 to finally include a few real pictures.

Disclaimer:
The below descriptions are for informational use only, if you are unsure about what you are doing when it comes to wiring then find a licensed electrician in your area to assist you. The money you pay will be worth the piece of mind you will get knowing it was done right.
Replacing Existing Switches:
Read the below description FIRST before removing any wires. It is often times difficult to determine which wire should go onto which terminal of the replacment switch.

Knowing the 'travelers' and 'point' of the existing switch will make replacment much easier'.

Glossary:
Line This is were the power (HOT and NEUTRAL) is coming from.
Switch Leg This is the wire that comes from what ever is to be switched. It could be a switched outlet, an overhead light, or recessed lighting.
Three-Way This is a switch that has three terminals (screws) on it, excluding the ground screw (if present). It is used to switch a light from two different locations.

This is the part that often confuses the novice ("Why is it called a three way if you only use two of them?").

One of the terminals will be a different color than the rest. This is the 'point' or 'common'.

Travelers On three-way switches they are the two like-colored terminals (screws). The wires that are connected to these terminals are referred to as the 'travelers'. In the diagrams below, the travelers will always be the RED and BLACK wires of a 14/3 cable.
Point This is the third (usually black) colored terminal on a three-way switch.
Four-Way This is a switch that has four terminals on it, excluding the ground wire. It is used between two three-way switches to control a light from a third (or more!) location.
14-3 This is a three conductor (14 gauge wire), excluding the ground wire, cable. The wire colors are almost always RED, BLACK and WHITE.
14-2 This is a two conductor (14 gauge wire), excluding the ground wire, cable. The wire colors are BLACK and WHITE.

The ground wire is not shown in any of the diagrams. Check your local code requirements.

Move the mouse over the below descriptions to view a picture of the switch.

The Three Way switch in the picture has its travelers on the top.
The Point, in the lower left corner of the picture is a different color than the travelers so it is easily identified.

The Four Way switch in the picture has two sets of like-colored screws. Although its not easily visible, they back of the switch is labeled IN and OUT.
When you bring your 14/3 wire from both 3-way switches into the box, one set (meaning the red/black wires from one 14/3 cable) are connected to the like-colored screws (terminals), for example the black screws (labeled IN in the picture). The travelers from the second 14/3 are connected to the copper colored screws.

Switch
Key: Three Way - Key
The Standard Method
This is the way I was taught Standard Three Way Diagram
You may be wondering what makes a three-way switch work. If so you are not alone. The internals of the three way switch does all the work. When the switch is moved from one position to another, the internal connection switches from one of the traveler terminal to the other.

Find the labels Internal Connection in the diagram above. The light is off.

Now, in the diagram below the Internal Connection of the second switch has been "thrown" which completed the circuit turning the light on.

Follow the circuit from the black LINE side through the internal connection in the switches to the switch leg.

Standard Three Way Configuration #2
Different Configurations
Now the only other thing to consider is different configurations of where the switch leg and line come into the switch boxes.
This diagram shows how to wire things up when both the switch leg and power come into the same box.

What may concern you in this diagram is that black of the switch leg is connected to a white wire. This white wire will be live when the circuit is complete. A white wire carring line voltage is only "code" (that is, allowed by the electrical code) when it is being used in a switch situation. It is also the most common method used by electrians to identify a switch leg.
Note: When you see a black and white connected one COULD be a switch leg.

Note that the 2000 NEC code now requires that this wire be marked (usually with black tape) as to not confuse people.

Note2: I received an email (09/2003) that stated that updates to the code require painting or marking with permanent marker the white wire when used in the above fashion.

Three Way with Line/Switch Leg in Same Location
The next case is when the Feed and switch leg all come into a separate box (for example a ceiling box for an overhead light).

A switch leg (14/2) is run from that box to one of the three-way switches.

Three Way - Line/Switch Leg in Seperate Box
4-way Switches
Now lets throw a four way switch into the picture.

The terminals on the four way switch will be labeled to let you know which ones to connect to each leg of the travelers. The third (white) wire in the 14/3 is connected up as to just pass through.

What happens when the four way switch is flipped is the internal connections are reversed. That is, if, internally:
S1's RED was connected to S2's RED and
S1's BLACK went to S2's BLACK (as shown),
switching the four way will cause S1's RED to go to S2's BLACK and S1's BLACK to S2's RED.
That will either make or break the circuit (in the diagram, it will complete the circuit).

Three Way with four Way