HI - thanks for the feedback. I was trying to put a hole through a few other solids (magenta here) and then build a 1/8" thick walled surround (grey here) that connects the two holes. I built the void as a solid because the void has to be a precise size, then used the SOLID->OFFSET command to create a 1/8" larger solid, figuring I’d then BOOLEANDIFFERENCE the two to get the walls, but…no.
There are other ways and/or sequences to do this, sure, but it is easily accomplishable in Autocad (gasp) and since Rhino is SO MUCH BETTER in just about every way, I guess I expected it to work here, too, and was surprised that it doesn’t.
As seen in Autocad2018 - a solid with a void as a valid object.