Abstract: A window frame is made of a plastic material which is secured together by utilization of corner key pieces at each of the four corners joining the header and the sill with a pair of jambs. The corner key pieces may be initially stapled or screwed to the frame members to create a stable unit prior to the permanent securement of the various members by means of ultra-sound welding.

Abstract: A securing device for casement windows or the like includes an abutment member secured to the master frame in the path of motion of an engaging member. The abutment member extends away from the master frame a greater distance at the end of the abutment member nearer to the inner side of the window. The engaging member is mounted to the casement frame and extends away from the casement frame a greater distance at its side closer to the outside of the window. Both the abutment member and engaging member include non-planar contacting surfaces which mate when the window is in its closed position. This arrangement of the abutment member and engaging member also prevents the casement frame from bulging away from the master frame under wind pressure. The securing device is mounted along one side of the window.