Whatever the goal/field object I think is triangular. 3 casters in each corner and the 3/4 plywood is probably for the base.
I also noticed a mistake on the BOM... It lists 2x4x8 twice on the list. One has the quantity of 5 and the other is 1. Since the lumber dimensions are listed in order from least to greatest, the other dimension should probably be 2x8x8.
I am almost positive all this stuff makes up several different parts of the field, not just one. I mean how could 3 casters support all this weight, unless the casters are used for something totally different......
Bad Brad