(stile, sill, rail) A lightweight timber frame covered with scenic canvas. Now usually covered with plywood or hardboard and consequently not so lightweight. Most theatres have a range of stack flattage made to a standard size, and re-used many times. A Rail is a horizontal batten within a flat. A Stile is a side or vertical piece within a flat. A Sill is the bottom rail of a flat. See also Book flat.