This is what I cut with a cnc router, the two large pieces are the left and right sides of the trailer and all the little numbered pieces fit between the small rectangular traditionally cut ribs. These numbered parts attach to the side wall to properly space the horizontal ribs and then the parts you see "U" shaped cutouts on make a middle spar. The "U" cutout was also done on the horizontal parts so they all fit together like puzzle pieces. A little bit of glue, stapling, and screwing, and you get to the next photo in just a couple hours. It's the most fulfilling part of the project because things come together so quickly, but wow is it such a small portion of the whole project.