Sharon's quilt HALO is a weighted ring (8" in diameter) that has a rubbery coating which causes it to grip the fabric, rather than slide over it. The weight helps control the three layers of the quilt sandwich so that it moves as a unit under the machine needle for free motion quilting on a domestic sewing machine. I think it is especially helpful for beginners who might have trouble controlling the quilt around the needle, but it's also really good for anyone with hand issues like arthritis or carpal tunnel syndrome. I find that my hands don't get as tired or my shoulders as tense when I use the halo, and I've been machine quilting on a DSM since 1992.
To use it, just position the quilt under the needle where you want to stitch, then slip one side of the halo under the presser foot so that the machine needle is in about the center of the halo. Just a little downward pressure on the sides of the halo will allow you to move the quilt where ever you need to stitch. When you get close to the halo, just stop the machine and lift the halo up to re-position it then keep sewing.
Check out Sharon's YouTube video:
http://www.youtube.com/watch?v=SpmMYIDCrZw