The term "single bed" or "spring mattress" is commonly used to describe a frame bed. A frame bed is constructed so that the lower coil housing rests in the wooden frame, and it can have one or more coil housings that work together. When you look at a frame bed, you only see a spring mattress, and it is on this mattress that you place the mattress topper. Due to its construction, a frame bed provides a more stable comfort compared to a continental model.