A storm window or the like formed of plastic extrusions with a frame, glazing sheet, and lock strips pushed into grooves of the frame, holding the glazing sheet between the frame members and lock strips. A removable frame formed of frame members joined together at the corners by corner fasteners with arms which push into slots of the frame members. Mounting clips for mounting the window to a support surface, with variations for flush mounting and recess mounting, with the mounting clips snapping into grooves in the lock strip.
Wall assemblies useful for a wide variety of different applications can be economically constructed utilizing extruded polymer panels shaped so as to have sloped positioning walls located adjacent to interlocking connecting elements at their side edges. The connecting elements are shaped so that the connecting element along one side edge of one panel can be pushed into engagement with a connecting element along another side edge of another panel through the use of a tool pressing against the adjacent positioning walls when the side edge of the first of the panels is located over the side edge of the other panel.