Rim Set mounts, are metal mounts, that hold rhinestones and jewels, creating an enclosed, finished look. The rim set is set from the top, over the rhinestone, crystal, the prongs are pushed through the fabric, and than they are bent, folded inside the fabric. The rim set frames the stone. As the prongs are inside the fabric, if not properly set, they can scratch the skin, or a different garment (in case of a jacket), an inside lining can take care of it and also create a clean look instead of a bunch of metal pieces.
The Rope and Fluted rims are specialized rims and may not fit all stones. They have a thicker frame.