From the Stitch Description: Razor Shell is a simple Shetland pattern forming lace ribs. It can be made in a variety of widths, on multiples of 4, 6, 8, 10, 12, or more stitches; or in a combination of these - for instance a wide rib alternating with a narrow one, etc. The tiniest version, a multiple of 4, when repeated across a fabric makes a Lace Rib Mesh. The most commonly used traditional forms are the wide 10- or 12- stitch ribs.
Location of Stitch: Page 206 from A Treasury of Knitting Patterns.