T.D.
I hope this makes sense, I will try to explain it as best I can.
This will work on the arch window that is separate from the rectangle ones below, the ones that have their own ledge.
If you go to Home Depot/Lowes, there is some molding that is painted white, it's not wood, it's very bendable and quite long. You can cut it with a knife or box cutter....... cut it to the length of the arch. Buy some sheers and slip it onto the molding, (the top of the sheers should already be stitched to slip into a rod). When you stick it up in the window the fabric will all come towards the middle. Bunch it up and put a rubber band to make it like a flower looking thing, fluff the sheers to hide the rubber band. It looks pretty good, and is SO cheap to put together.
~ t