e which does not extend the full height of the rack bar the small segment 54 b connects the segment 54 a to the rest of the rack bar 44 when the rectangular segment 54 a at the end 46 is inserted through the keyway 52 the smaller rectangular segment 54 b having nominal height and width dimensions of u00bd inch resides in the slot the diameter of the circular cutout 52 c enables rotation of the rack bar when the larger rectangular segment 45 a is extended through the keyway to the rear side 24 r of the plate for example the cutout 52 a may have a u00be inch diameter once the rack bar is rotated into a desired rotational position it is slid downward in the keyway to secure the rack bar in a lower rectangular portion of the keyway slot i e below the circular cutout a second feature of the rack bar 44 is provision of a stop 58 at the second end 48 along an upper surface 60 thereof the stop impedes movement of the material off the end 48 when being placed on the surface 60 the combination of the stop 58 and any slope provided to the rack bar also help keep the material in place during transport to impart a slope to the installed rack bar relative to the plate 44 the mating feature may be formed at an angle with respect to the vertical orientation of sides of the cutout the rack bar 44 may be made of aluminum other metal a plastic or a composite material further the rack bar may have holes in the bottom or sides to provide anchor points for rope straps bungee cords or.