made of 100% scrap wood found in my garage and thrown together pretty quickly
here is a pic of how i attached the rail to the wood:
just to give an idea about how i built it:
9 ft long:
the rail itself seems mostly stable for how i put it on the wood. it does have a tiny wobble but it shouldnt be a problem. if wobble does become a problem i could probably fix it with some liquid nails or just by putting some shims on either side.