Fine Line™ Straight Quilting & Applique Ruler
The difference in application is the resistance strip on the underside of the ruler base.
The applique ruler has a softer resistance strip for working around delicate stitches and raised motifs in blocks and borders.
The regular ruler has a resistance strip which is the "hook" side of industrial Velcro. This strip keeps consistency with different battings used in quilting, from low loft to high loft. The tooth bed on the industrial Velcro is deeper, thus keeping you in control on any thickness of your quilt regardless of loft.