Structural part made of plastic material

Claim 1

A STRUCTURAL PART OF PLASTIC MATERIAL FOR ROOF COVERS, WALL COVERINGS, OR THE LIKE COMPRISING: PLATE-LIKE STRUCTURE HAVING A PLURALITY OF EDGE PORTIONS AND PROVIDED WITH APPROXIMATELY U-SHAPED HOOK MEANS WITHIN THE AREA OF TWO EDGE PORTIONS EXTENDING TOWARD OPPOSITE SIDES OF THE PLATE-LIKE STRUCTURE, SAID HOOK MEANS INCLUDING FREE LEG PORTIONS OF SUCH SHAPE THAT THE WIDTH OF A RESPECTIVE HOOK MEANS INITIALLY DECREASES SLIGHTLY IN THE DIRECTION TOWARD THE END OF THE RESPECTIVE FREE LEG PORTION AND THAT AGAIN INCREASES, AND THE WIDTH OF THE HOOK MEANS BEING SO DIMENSIONED THAT SIMILAR STRUCTURAL PARTS MAY BE INTERCONNECTED BY THE HOOK MEANS THEREOF, THE PLATE-LIKE STRUCTURE INCLUDING TWO IDENTICAL PLATE LIKE PARTS COMBINED WITH EACH OTHER TO FORM A STRUCTURAL PART, EACH OF SAID TWO IDENTICAL PLATE-LIKE PARTS BEING PROVIDED WITH A RELATIVELY WIDE HOOK MEANS POINTING TOWARD ONE SIDE AND WITH A RELATIVELY NARROW HOOK MEANS POINTING TOWARD THE OPPOSITE SIDE, THE OUTER SURFACE OF THE FREE LEG PORTION OF A RESPECTIVE NARROW HOOK MEANS CLOSELY ABUTTING AGAINST THE INNER SURFACE OF THE FREE LEG PORTION OF A RESPECTIVE WIDE HOOK MEANS WITH THE INNER AND OUTER SURFACES COVERING ABOUT EQUAL AREA, AND THE SPACE BETWEEN THE TWO PLATE-LIKE PARTS BEING FILLED WITH INSULATING MATERIAL.