Got one! Mine is 18 x 20 and it is the steel/aluminum kind. In my area you always see them advertised on the side of the road or at a place of buisness. You can get them in a variety of colors to match your house also. If your not sure what I'm talking about I may be able to find you a link. They attached it to my asphalt driveway with 2ft re-bar with a nut welded on the end to stop it from going throught he hole on the base piece. They just drove it through with a sledge hammer until it punctured the asphalt then sunk in the ground. I love it, provides alot of shade and helps keep the cars a bit cleaner from "light" rains.
I didn't install it, but I had it a year and have done no maintenance.
