I downloaded the plans from here. I suspected that it was for pushing the frames up out of a super when extracting, but I can't figure out the purpose of the different heights.
Yes, the infamous dumping board. We discussed this, in detail, a few times and no
can figure it out. I tried a net search once time and came up with nothing.
I tried a few emails and the outcome was the same. I say we ask Barry to remeve the drawing.
Here's my shot at it. I know I've spent way too much time looking at it.
I think it's made to work with the honeycomb uncapping tank and the homemade super (different plans).
My guess is that you turn the honey super upside down over the upper "shelf" in the dumper. 1'8" is just the right length to fit a super long ways. When you slam down a super, the handhold cleats should hit the sides of the dumper before it bottoms out allowing the frames to dislodge and stand upside down.
The next step sounds clumsy, but it's the only way that makes sense (at least to me).
If I read it right, the top of the steel tank sits 10-3/8" (15-3/8"(tank height) minus 3-1/2"(rail height) minus 1-1/2"(2x2 height)) above the 2x2 brace across the end of the tank frame. If the metal tank is slid against one of the end 2x2s (the tank is only 6' long vs. 6'-4" between the 2x2s), the dumper could be stood on end on the 2x2 with the lower "shelf" against the end of the metal tank and the frames stacked horizontally across the metal tank. Then, with the rounded corners to help, you could flip the dumper all the way upside down on top of the metal tank. This would put the frames right side up with the ends of the frame top bars resting on the 1" wide lips of the tank and the rest of the frame hanging in the 1'-6" opening in the top of the tank. This would provide a place to hang the frames until they are uncapped.
Only one problem that I see. The capping basket frame is only 1'2-1/2" x 1'5" so it won't hang in the 1'6" opening of the of the tank -- at least not without turning it diagonally to catch the corners.
Anyway, that's my story and I'm sticking to it.