Abstract: A tiltable window sash mounted in a channelled window frame having a T-shaped bar projecting from the sash into the window frame channel, with the wings of the T-Bar engaging the inside of the window frame channel so that sash to frame alignment is maintained. The bar simultaneously provides a pivotal axis about which the sash is tilted. The bar engages a sliding pivot shoe located in the window frame channel to provide a guide for sliding of the sash. The pivot shoe has a cam operated dial acting brake; the cam is coupled to the T-shaped bar, so that the sash is tilted; the cam operates a first brake preventing sliding of the tilted sash, and when a predetermined angle of sash tilt is reached, a second brake is operated by the cam preventing further tilting of the sash, thus supporting the sash in a tilted position.