Here we see a bottom view of the boxcar. Trucks are Kadee HO-gauge archbar. A little small, but on a freight car this size, they work fine. The box-form between them is to hide part of the weights. In the model railroad world, they decided to enclose the brake parts to keep saltwater from damaging them, and access them through a hatch in the car's decking.

Still have to add details and a roof to this car. Needs stirrups, latch mechanism for the door, some kind of cross-bar detail for the door (ever notice that most wooden boxcar doors had some kind of board running cross-wise or diagonal across them? That kind of thing), a brake wheel, facia boards for under the roof, and so forth. Oh, and paint.