"Clings" to smooth sewing surfaces (no taping) so it's always in position ready to sew ANY 45 dgree angle accurately. You will appreciate the Fabric Alignment Key and 1/4" and 5/8" seam guides. It's color-coded for different techniques. It does NOT need to be removed to access drop-in bobbins or to move your machine. A staple, must-have notion for every quilter.