I use an extra piece of coroplast wrapped in flecce. The coroplast is cut to fit loosely on the floor of the ramp (loosely because I will be wrapping two layers of fabric around it. The final product is snug), and also has a 2-inch flap that attaches to the loft coroplast and tucks under the fleece flipper (although I'm sure it can work this way even if you don't have flippers). I don't have a specific cover, but I use safety pins on the back to secure a layer of uhaul and a layer of fleece. The piece then attaches to the loft, and sits flat in the ramp. Since the ramp itself is coroplast with a grid frame, the pins are completely unaccessible to the pigs, so there is no chance that they will get pricked. Let me know if this doesn't make sense and I will take photos.