In this post we'll go over wiring 3-ways and 4-ways, below are some diagrams with explanations:
Above is a 3-way system. A 3-way system is intended as a way to provide two different switching locations to the same light or lights: i.e. your living room has two entries and you want to be able to operate the light from either.
3-way switches have 3 power terminals and a ground terminal(green screw terminal):
-One terminal is designated for your hot wire or switchleg and is usually a different color than the other two.
-The other two terminals are your travelers which essentially are a set of switchlegs between switches that allow switching from 2 different spots.
As you can see above it's a pretty straightforward system you bring your power in to either of the switches(but not both) tie a set of travelers between the switches and bring your switchleg out of the other switch, simple as that.
Below is a 4-way system.
A 4-way system allows 3 or more switches to control the same light or lights:i.e. a large conference room with 3 or more doors and you want the lighting controlled from any of them.
4-way switches have 4 terminals and a ground terminal:
-These 4 terminals are two pairs that break each traveler(see above diagram) and usually identified by two different colors if not you must identify them with a multimeter.
4-way switches always go between 3-way switches as their only job is to break or make the travelers.
*Neutral conductor gets carried through all the boxes to the fixture.
*Never use a white wire for a hot or switchleg unless it is marked as so.
*The switchleg is the wire that goes from the switch to the light fixture.