Those plastic rings are used in knitting to mark the start or ending of a pattern--at least that is what I use them for. They come a bunch in a bag.
I also hang my Christmas quilted wallhanging from the top of the stair railing with yarn---pull tight and no one can see the yarn that I use. One could also use invisible fishing line so that the corners don't sag and then no one can see a thing---drives 'em crazy.