A single sofa bed is a piece of furniture that can be used as both a sofa and a bed. It typically has a foldable or convertible mechanism that allows the seating area to be converted into a sleeping surface. The bed is usually a single size, making it suitable for one person to sleep on. They are often used in small apartments, guest rooms, or other spaces where a full-size bed would take up too much room. Some popular styles of single sofa beds include pull-out couch, futon, and daybed.