Still intrigued by this
Although I have no experience in that area I can see the argument for a supply drop 'chute, for the round one at least, but I wonder why the added complication of a lubricated swivel bearing. Surely it wouldn't be necessary in that case?
The shape of the square one is puzzling in that it looks as if the shaped corners might be designed to fit onto a four-legged frame of some sort, and the rims of the holes appear to be thickened, perhaps to avoid chafing a cord or cable passing through them.
Even more annoying is the nagging feeling in the back of my mind that I've seen something like the round one before . . . somewhere
Mike.