A few years ago I built one with 4 layers of carpet. It is 7 foot wide and 8 foot tall. Used a 1" X 3"s to support and separate the carpet, (the bar). I then built a frame legs out of 4" X 4" post, a header out of 2" X 10" and additonal lumber. Using the header I screwed on scrap angled wood from making a stair stringers. These angles support the small roof that is shingled. I have placed two sheets of plastic on the front and back which helps keep the sun off the carpet. The carpet bar is supported by chains off the header.
This is used as a back stop only.