I know that some decks have posts you can remove and use in a slot to secure the belt until the rear cover is put back on. then you remove the screw to pop the belt on and put it back on the rear cover for next time. That's what I did with that screw. Not sure that was its intended purpose and it's been a while since I put belts on my Conion but I remember that screw and remember removing it and using it in another hole temporarily to help me with getting the belt on the motor easier