opposite side thereof so that the row of holes 124 is axially spaced from the row of holes 122 and holes 124 are also longitudinally offset from holes 122 holes 122 and 124 extend from the top surface of tongue of 116 to the bottom surface thereof another row of vertically spaced through holes 126 fig4 6 is formed in vertical segment 80 of crossbar 74 extending from the front to the rear surface thereof and positioned on the one side of web 72 and plate 40 likewise another row of vertically spaced through holes 128 fig6 is formed in vertical segment 80 of crossbar 74 on the other side of web 72 and plate 40 in the exemplary embodiment each of t bars 70 and 92 is formed in an extrusion process the extruded t bars are bent to form their respective arcuate segments and l shaped and s shaped configurations typically at room temperature a portion of web 93 is cut off or otherwise removed from the corresponding section of crossbar 95 to form tongue 116 as previously noted once the extruded t bars are in their appropriate l shaped and s shaped configurations they are heat treated in order to provide additional strength and eliminate internal stresses caused by the bending process the heat treated t bars are subsequently welded to the l shaped and s shaped edges 50 and 58 of.