Miriam
The pipes are not threaded. Just held together with the set screw couplings. I could have used threaded plumbing pipe but then the frame would have been heavier. If this EMT pipe doesn't hold up I'll just go back to PVC pipe.
If your asking about that wooden dowel attached to the rubber strap the link to Flickr will show how I tied things together.
Mike
I did use 1/2" EMT. I don't have a pipe bender so I bought the corners already bent. If I had a pipe bender I would have used it. That would have cut down on some of these couplers making the frame a little less wobbly.
These set screw couplings were not designed to be used the way I'm using them. I had to drill a hole in the pipe for the set screw to go into the pipe to keep the pipe from pulling apart. And on one side of the coupling I had to drill out the set screw hole so I could use the pins to be able to take this frame apart.
Even though the connection won't pull apart, it's not a tight fit. So one side of the frame has to be attached to the camper and the other two corners have to be tied down with guy ropes. When you do that it doesn't move.
Some of the thumbnail pics have text explaining the pic. Just click on the pic to see the text.
http://www.flickr.com/gp/12715809@N07/m1N457