Does anyone know what this is?

gryghst

It goes over the cross bow end just over the drivers head. There is one one both sides of the bow support. They get pushed out of position when you close the top. You need to cover the ends of the front cross bow, it will wear through the top from the inside given enough time. A heavy 2"×4" velcro patch works well. You can pick them up at any Ace hardware store. They come with a very sticky side which holds on the ends of the cross bow.