The backstool represents an intermediate step between the development of the stool and the chair. A simple three-legged turned stool would have its rear leg extended outwards and a crossways pad attached. Backstools were always three-legged, with a central rear leg.
Turned backstools led in turn to the development of the three-legged turned chair, where the backrest was widened and supported by diagonal spindles leading down to extensions of the front legs. In time these diagonal supports became larger, higher and more level, leading to the turned armchair design.