"F", "C", "H" and " L" angle  extrusions are available in well equipped hardware and big box stores. They can be rivited or bolted to the trailer ribs or slats. Acyrlic window panels are usually simillarly sourced, but if you want the best durability, the Lexan polycarbonate is far superior, albiet at a higher cost. Glass companies are also a source of the window sheeting, and can custom cut each piece as it is needed.

Both materials can be cut at home using common wood working tools, however more care should be used when power tools are applied to the acrylic materials. Any binding of the cutting tools can result in the material shattering. The Lexan is about fool proof and is very difficult to damage. If any bolts will penetrate the windows, drill the holes oversize so the bolts don't stress the materials.

Adding the windows is a relatively easy DIY project.