yoke has a cross bore 270 for receiving a rod 274 the rod 274 is supported at its opposite end by the elevation adjustment assembly 140 b the rod 274 supports a rear portion of the inside frame 80 an adjustment knob 282 is rotationally fixed to an end of the threaded rod 260 to turn the threaded rod by hand the threaded rod 260 includes a shoulder portion 260 c adjacent to the flange 126 a of the outside frame 120 when elevation adjustments are completed the locking knob 262 can be elevated on the threaded region 260 b by turning the knob 262 while holding the adjustment knob 282 to prevent the rod 260 from turning the locking knob 262 is elevated until the flange 126 a is tightly clamped between the shoulder portion 260 c of the threaded rod 260 and the locking knob 262 the threaded rod rotary position is thus locked and prevented from changing during operation as shown in fig9 the elevation adjustment assemblies 142 a 142 b support a rod 294 that supports a front portion of the sidewalls 80 a 80 b of the inside frame referring to fig4 c the height adjustment assemblies 140 a 140 b 142 a 142 b can be independently adjusted to level the conveyor 46 a series of.