Stop walking across a dark room to turn on the light. Install a 3-way switch and control lights from two locations.

Here is a typical three-way switch viewed from two sides. It has a total of four screws, the black one being the most important. By Tim Carter | Tribune Content Agency February 11, 2015 at 12:00 a.m.

Three-way switches are common at staircases, hallways or large rooms with multiple doorways. Most of the problems with these switches result from a miswired switch.

It also contains links to both my three-way and four-way switch videos. The PDF document also has several great photos of efflorescence and a link to a video I recorded about efflorescence.

Here's how to swap outdated three-way light switches for something much better.

The simplest setup is to have just two three-way switches control one light. A three-way switch has three screws on it, plus the green grounding screw.

Below, Donnelly tells AD how to wire a light switch with this simple step-by-step process for a single-pole light switch without zapping yourself along the way.