Sanding Films can be purchased at any hobby shop. They are used for finish sanding models before painting them up. If you want to add a smooth edge to your piece of kydex, this is the way to do it. They come in a variety of grits, and just like normal sanding, you start with the lowest number grit and work your way up to the highest, removing a LITTLE material with each step, getting smoother and smoother as you go. The finest films almost feel like paper they have so little abrasive in them, but they really polish the kydex nicely.