62 contain two matable slits 13 referring with specificity backing piece 60 preferably has a thickness of u215b inches u215b u2033 matable slits 13 are preferably u215b u2033 wide and u00bc u2033 deep preferably matable slits 13 are preferably spaced with 2 u215b u2033 spacing between edges of each slit fig9 illustrates a perspective view of support rod 12 in a preferred embodiment support rod 12 has eight matable slits 13 on its periphery with four on each of its longer sides support rod 13 also has rounded edges 71 referring with specificity support rod 12 preferably has a length of 7 85 u2033 a width of 1 u2033 and a thickness of u215b u2033 matable slits 13 are preferably u215b u2033 wide and u00bc u2033 deep matable slits 13 are preferably spaced with 2 u215b u2033 spacing between edges of each slit the distance from the edge of the outermost matable slit 72 to the top of the rounded edge 71 preferably is 31 64 u2033 and the radius of rounded edge 71 is 8 16 u2033 fig1 illustrates a perspective view of elongated support rod 80 in a preferred embodiment support rod 80 has ten matable slits 13 on its periphery with four on each of its longer sides and one occupying the center of each rounded edge 81 referring with specificity support rod 80 preferably has a width of 1 u2033 and a thickness of u215b u2033 matable slits 13 are preferably u215b u2033 wide and u00bc u2033 deep matable slits 13 are preferably spaced with 2 u215b u2033 spacing between edges of each slit.