When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Without these screws, your outer rails probably rattle a little bit because they are just hanging by the hooks. The washer centers the screw, and the screw locks the rail in so they are secure and in the correct position with little "play", otherwise just sitting on the hooks the rails can float side ways a little bit.
When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.