A Box On Wheels

In simplest terms, a caboose is nothing more than a box on wheels.  Sure, there's more to it than that, but essentially it's a box sitting on a frame with wheels underneath.

As the first step in my caboose construction, I started with the frame, using 6"x7" timbers as specified in the plans that I purchased.

Using scribed sheet stock, I cut the side walls and cut out the window openings.  Since this thin material tends to warp when painted, I also added some bracing to the inside of each wall.  I won't be detailing the interior, so this doesn't need to look pretty.

With the floor in place, and the two side walls propped in place, you can see that this is indeed nothing more than a box sitting on a frame.