I am a big believer in using grow tunnels or a simple hoop greenhouse made out of PVC pipe or plastic electrical conduit covered with plastic film. They are easy to build, inexpensive, and allow tomatoes and other warm season crops to fully mature in our cool Alaska summers. I haven' been able to find anything locally designed to attach plastic film to a tubing frame. I have used large spring clamps and paving bricks to hold down my plastic film, as you can see in the photo above. I recently found these handy plastic clips on Amazon.com and ordered some to try out. Stay tuned for my full review as soon as they arrive. You can click on the image or follow the link below if you are interested in trying this product yourself. They come in bags of 10 clamps for $9.95 plus shipping.