Some of my boxcars have open doors (some are movable and some are permanently opened). Having an empty box car isn't very entertaining. I decided that some 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).
I then covered all six sides of the block with stripwood. I used scale 1x5 boards, cut to size and glued with yellow carpenter's glue.
Crates come in all different sizes, shapes, and configurations. 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 the next photo.
One little drop of glue was used to hold these in a box car.