Method and apparatus for framing plastic material

Claim 1

A STRUCTURE FOR ANCHORING FILM-LIKE SHEET MATERIALS HAVING A LOW COEFFICIENT OF FRICTION IN A FRAME COMPRISING A FRAME ELEMENT HAVING A FIRST RESILIENT WALL SPACED FROM A SECOND WALL, SAID WALLS PROVIDING ANAPEN SPACE THEREBETWEEN FOR RECEIVING AN EDGE PORTION OF SAID SHEET MATERIAL, A RIB ON SAID RESILIENT WALL EXTENDING INTO SAID OPEN SPACE AND PROVIDING A LOCKING SHOULDER, AND A NON-COMPRESSIBLE, SUBSTANTIALLY RECTANGULAR SPLINE IN SAID OPEN SPACE HAVING A FIRST SIDE WALL ADJACENT SAID SECOND WALL OF THE FRAME ELEMENT AND A SECOND SIDE WALL LOCATED, ADJACENT TO AND EXTENDING PARALLEL TO SAID RESILIENT WALL OF THE FRAME ELEMENT, SAID SECOND WALL CARRYING A SUBSTANTIALLY RECTANGULAR RIB PROVIDING A LOCKING SHOULDER WALL EXTENDING OUTWARDLY PERPENDICULAR TO SAID SECOND WALL OF SAID SPLINE AND ADJACENT SAID RESILIENT WALL, SAID SPLINE RIB HAVING A SECOND WALL ADJOINING SAID LOCKING SHOULDER WALL AND EXTENDING PARALLEL TO SAID SECOND WALL OF SAID SPLINE AND RESILIENT WALL OF THE FRAME ELEMENT AND A THIRD BOTTOM WALL ADJOINING SAID SECOND WALL OF THE SPLINE RIB AND EXTENDING PERPENDICULAR TO SAID SECOND WALL OF THE SPLINE, SAID SPLINE AND SPLINE RIB COMBINED BEING SLIGHTLY THICKER IN CROSS SECTION THAN SAID OPEN SPACE, AND SAID EDGE POR-