Cheryl: I don't know what would work in your case. In our trailer, the strings were strung about 1" apart parallel the length of the trailer. I know it was labor intensive because it was my job as a teenager to make a new canvas top for the trailer & re-string it too. Anyway, I don't know how close together the strings would need to be for your greenhouse. Hopefully not 1" apart! jb123 asks a good question: are you going to hold the sheeting to the frame, and how so? If the frame were wood, you could sandwich it between pieces of wood, top & bottom & nail.