The Square with a Vertical Slit shawl shape is one of shawl shape recipes in Shawl Geometry Book Two - a collection of fresh shawl shape recipes to add to your knitting library.

More about Shawl Geometry Book Two:
Starting from scratch every time you want to cast on a new shawl sucks.

But what if you had an easy to browse resource of shawl shapes?

A reference book of shawl shaping that laid out all the numbers, and all the calculations. Like a stitch dictionary, but for shapes instead of stitch patterns.

That’s what the Shawl Geometry Books are.

Shawl Geometry Book Two lays out knitting recipes for intermediate shawl shapes that we known and love, plus shapes that are a little more uncommon.

This book contains 45 shawl shapes, with 89 knitting recipes, all laid out in clear, straight to the point knitting instructions, so that you can cast on right away.

The shapes available in Shawl Geometry Book Two include:
Log Cabin Square, Square with a Vertical Slit, 3/4 Square, and Exaggerated 3/4 Square, Rectangle #1, Rectangle #2, Bias Rectangle, and Asymmetrical Bias Rectangle, Bias Triangle, Exaggerated Bias Triangle, Three Point Triangle, Triangle with Exaggerated Wings, the Curved, Bias, Asymmetrical Triangle, Right Triangle with a Center Back Panel, and two methods for shaping Faroese Style Shawls, Side to side Trapezoid, Top-Down & Bottom-Up Trapezoids, Elongated Diamonds, then a Ribbon Variation, an Arrow Variation, and a Zig Zag Variation on the Elongated Diamond. Plus Hexagons & Octagons knit flat, and Hexagons & Octagons knit in the round, Octagon Doughnut, Octagon Doughnut with a Slit, 3/4 Octagon Doughnut, and 1/2 Octagon Doughnut, the Wedge Doughnut, Wedge Doughnut with a Slit, 3/4 Wedge Doughnut, and the 1/2 Wedge Doughnut, and finally the Pi Doughnut, Pi Doughnut with a Slit, 3/4 Pi Doughnut, and the 1/2 Pi Doughnut, Eight Equal Wedge Crescent, Eight Unequal Wedge Crescent, Six Equal Wedge Crescent, Six Unequal Wedge Crescent, Four Equal Wedge Crescent, and finally the Four Unequal Wedge Crescent.
(for a visual, see the third photo)

For more information about Shawl Geometry Book Two, and the other books in the series, see: http://www.hollychayes.com/shawl-geometry/