Abstract: A window sash construction is disclosed for wood framed windows in which a particular stile-rail and check rail member configuration is utilized to adapt a given sash to both vertical double hung and horizontal sliding installations, each sash unit being constructed with a common stile and rail sectional configuration such that all stile and rail members may be provided by two sash member types differing only in having two different end configurations and a common check rail shape in oder to assemble the universal sash units. A reversible common check rail configuration is also provided such that the sash units can be oriented in any mating arrangement while obtaining a proper seal.