Some of my box cars have open doors (some are movable and some are permanently opened). Having an empty box car isn't very entertaining. I decided that a few crates might be a good load (perhaps representing a less-than-carload load). I built a handful of crates using some blocks of wood as starters. This first photo shows some blocks cut to size using the table saw. Since I was dealing with about 1/2"-square blocks, it is a bit dangerous on the table saw. Since then I have found Hobby Lobby carries a bag of already cut blocks of wood about the same size. That made the process go a lot quicker, and safer (no table saw needed). The size doesn't really matter, as crates come in sorts of shapes and sizes; whatever it takes to fit around the content.
I then covered all six sides of the block with stripwood. I used scale 1x5 boards, cut to size, and glued with a very thin coating of yellow carpenter's glue.
I glued a set of boards along the top and bottom edges of the crates. A diagonal outside brace was added to make the familiar Z-shape. You can see the before and after in this photo.
One little drop of glue was used to hold these in a box car, so that can still be broken off if no longer needed. Normally, loads would be properly fastened-down and stored more efficiently, but, then again, railroads wouldn't run the cars with the doors open. So, this model might be one set at a team track of freight station being loaded or unloaded.