as illustrated in fig4 and 5 this ledge provides strength for the sides of the pan as well as a support for the expanded metal screen for supporting the pan rollers 32 and 33 at one side of the pan roll on the flange 14 of one i beam and rollers 30 and 31 at the other side of the pan roll on the horizontal surfaces of the flange 16 of the other i beam it is essential that these rollers not be permitted to slip off this horizontal surface and that the pan be maintained in its orientation so that the sides 23 and 24 maintain generally parallel to the i beam the rollers 30 31 32 and 33 are rotatable on bolts shown generally at 42 in fig3 and 6 and inasmuch as each of the rollers is similarly supported only one need be described in detail the rollers are preferably plastic although other materials can be used and rotate on a sleeve supported on a bolt 42 and drawn tight against a vertical plate 41 the vertical plate 41 is welded at the end of a bracket 34 the bracket includes a flat plate 40 which lays flat against the end wall of the pan as shown in fig1 a bracket is provided for each of the rollers with the brackets being shown at 34 35 36 and 37.