Today I would like to explain the intended function and use of the double door. The double door, a system of two standard-width doors, placed side-by-side, is intended to allow two-way traffic to pass through an opening, avoiding bottlenecks. It dates back to ancient Egyptian times. There are paintings of double doors on the tombs of the Pharoahs. It works like this: no matter which side of the door you’re on, you use the door on your right. Double doors may swing in both directions, may slide out of the way for you automatically, or may only open in a single direction. Nevertheless you use the one on the right. Anyone passing through the same opening from the other side uses the door on their right. And guess what? That’s your left! Isn’t that amazing? You can both pass through the opening at the same time without having to stop for each other!!! Genius!