The phrase "one's double bed" refers to a standard size mattress and box spring combination that is large enough for one person to sleep comfortably. It typically measures 39 inches by 75 inches, although sizes can vary slightly depending on the manufacturer or country of origin. The term "double" indicates that it is designed for use with two people, but since most people only need a single bed, they often opt for a double size to have more space and comfort while sleeping alone.