The first type of window that could be opened was a piece of glass in a wooden or metal frame, hung on hinges. They originated in Britain and Germany, where it was customary to have them open outward. The French, always wanting to be different, began to use the same type of window, only theirs opened inward. None of this, however, really explains why American architects decided to name glass doors that opened outward onto balconies and porches, "French doors."