lip 112 of the horizontal channel 110 the cone shape of the holes 111 allows the block 100 to find its own seat the top portion 101 also has a horizontal shallow channel 114 formed across it from side 105 to side 105 said channel 114 resulting in a horizontal forward channel lip protrusion 115 and a horizontal rearward channel lip protrusion 116 the vertical connecting flange 30 has two parallel side by side holes 39 formed therein below the junction line 36 each hole 39 is to one side of the longitudinal central portion 38 of the vertical connecting flange inner surface 33 the vertical connecting flange 30 also has two parallel wedge shaped blocks 92 formed on its inner surface 33 on each side of the central portion 38 over the holes 39 each wedge shaped block 92 has a hole 93 formed therein each wedge shaped block hole 93 extends from the vertical connecting flange hole 39 over which the block 92 is positioned inward and upward at a 45 u00b0 from vertical through to an inward and upward facing block surface 94 each fastener 91 is inserted into each side of the vertical flange hole 93 of the vertical flange wedge shaped hole 93 from the inward and upward facing block surface 94 through the respective vertical connecting flange hole 39 into and through the respective block hole 111 and exiting from the block.