slightly larger than the ridge so that the ridge of one panel 10 can be inserted into the groove 26 of another panel when the panels are mounted adjacent one another as shown in fig2 groove 26 and ridge 24 are offset towards the outside wall 14 seals are created at the flange and groove connection between the two panels in addition the flange and groove are positioned on the sides of the extruded panels such that when the panels are positioned adjacent to one another and fit together the side walls of the body structure is smooth it is contemplated by the present invention that the panels may lock together simply by the action of the flange of one panel engaging the groove of a second panel alternatively it should be understood that adhesives may be placed on the sides of the panels between two adjacent panels where the flange and groove engage or the seam between panels can be welded other suitable methods of connecting panels to one another or combinations thereof are contemplated it is also contemplated by the present invention that no flange or groove be present on the panels and that the panels are substantially smooth on all sides the adjacent panels could be placed adjacent to one another.