JAY DWARKADHISH ENTERPRISE French Doors, also known as double doors or double windows, are a pair of glass doors usually opening from the back of a house into its garden or onto its balcony. This concept of opening both sashes fully without seeing a centre obstruction has influenced French architecture since the 17th century. The whole grace and dignity of many European buildings was based on this majestic design principle. Modern fenestration adopted the uniqueness of French doors and French windows, mainly upgrading the design for high performance glazing and sophisticated locking devices whilst retaining the original character.