A couple of weeks ago, someone asked me why hinges traditionally come in pairs. I asked two of my favorite hinge experts - Matt Bouchard and Bob Jutzi, and they both gave me a variation of the same answer. In the 17th and 18th centuries there were 2 hinges on a door, so they were sold in pairs because you'd never use just one. In the early 1950's it was determined that a 3rd hinge would supply additional support and that became the standard. Our industry called that "a pair and a half" of hinges. There's some great hinge history at www.hardwaresource.com in case there's other hinge trivia you've been wondering about.