Daybeds typically feature a back and sides and come in Twin Size (39 in × 75 in = 99 cm × 191 cm). Often daybeds will also feature a trundle to expand sleeping capacity.
Many of today's daybeds employ a linkspring as the support system for the mattress. The linkspring is a rectangular metal frame (roughly the footprint of the mattress) with cross supports. A wire or polyester / nylon mesh held in place by a network of springs lies across the top of the linkspring. The linkspring design provides support and creates clearance underneath a daybed for storage.
A recent development in infant beds is a bed that converts into a daybed by the removal of one side, ensuring the furniture is useful for more than a couple of years.