Abstract: A patio door assembly made up of two identical glazed panels with one panel slidable in a frame and the other panel fixed to one of the respective jambs of the frame. The fixed panel is mounted on a false rail on the sill of the frame while a false mullion member and a sash block are provided which are easily removable to allow the fixed panel to be fixed to the other jamb of the frame. The sash block has a reversible insert which makes it conform to either position of the fixed glazed panel.