When I was a kid, I had some of these really cool poster hangers on my wall and on the door to my room. They had a really simple but clever design that used the weight of the poster itself and a small roller inside to clamp down and hold whatever you put inside the clip. Now that I have kids, I've looked online over the years for a similar product that I could buy for their rooms, but I've never been able to find them anywhere. The other day, I found a place that advertised them, but when I contacted them they said their vendor no longer made them.
Well, fine. I guess I'll just make my own. After tweaking it in Sketchup, printing a few prototypes to get the design right, and testing it out with some standard 1/4" vinyl tubing, I now have my model on Thingiverse. I hope you find this thing as useful as I do.