067. Freight CarThis is the sixth and final car in the train shown on the set's box art. It was also the simplest of the six to build. Note that there's no dowel shown sticking up through the upright piece.
I can't imagine just setting the piece on the car body. Perhaps its secured with a short dowel that would be entirely enclosed in the upright piece.
As I mentioned at the start of this miniseries, the Line Mar Construction Set only has enough pieces to build one unit of the train. One way to build the complete train is, of course, to use multiple sets. I preferred to use Photoshop.