From the Pattern Description: This is one of those interesting little patterns that make half a dozen different fabrics out of minor changes. The basic Tanbark can show either its right side or its wrong side, or it can be worked as a tweedy check by using one color for Rows 1 and 2, another color for Rows 3 and 4. Tanbark Variation can be used either in a plain color or in two colors; and it makes two different color patterns, depending on whether the contrasting color is introduced in Rows 1 and 2 or Rows 3 and 4. Also, the first two rows of the Variation make an imitation tuck, useful when changing from one color stripe to the next, and a pretty turning ridge for a hem.
Location of Stitch: Page 256 from Charted Knitting Designs: A Third Treasury of Knitting Patterns.