the window sash frame 10 consists of an upper extrusion 12 lower extrusion 14 left side extrusion 16 and right side extrusion 18 the extrusions are all made from vinyl by a process well known to those skilled in the art fig2 shows a cross sectional view of left side extrusion 16 the left side extrusion 16 consists of a pair of elongated opposed inturned u shaped flanges 20 and 22 which are connected to elongated rectangular flanges 24 and 26 flanges 24 and 26 strengthen the window sash frame and also provide a structure for mounting certain types of window hardware handles locks etc the rectangular flanges 24 and 26 have sides 24a 24b 24c and 24d and sides 26a 26b 26c and 26d sides 24c and 26c are joined by bridging flange 28 sides 24a and 26a form part of elongated longitudinal flanges 30 and 32 a second bridging flange 34 joins longitudinal flanges 30 and 32 extending generally perpendicularly from longitudinal flange 30 and generally towards longitudinal flange 32 are elongated barb flanges 35 and 36 extending generally perpendicularly from longitudinal flange 32 and generally towards longitudinal flange 30 are elongated barb flanges 38 and 39 each barb flange 35 36 38 and 39 has a straight edge such as straight edge 39a of barb flange 39 and toothed edge such as toothed edge 39b of barb flange 39 toothed edge 39b defines teeth such as tooth 39c on flange 39 tooth 39c consists of a bevelled leading edge 39d and a horizontal straight edge 39e it will be appreciated that four locking recesses 50.