This particular pattern comprises a garter tab cast on. I mentioned this cast on in a previous post and have been developing a more thorough understanding ever since. At first, the garter tab looks to be another example of tricky knitting magic, a technique I would group in with Judy's Magic Cast-On and the Magic Loop, but I have come to understand that this cast-on method is fairly simple. Further, the garter tab is a high-utility start for a triangular shawl, for it creates a seamless line across the top edge of the shawl, instead of allowing for a gap or dip in the knitting (see images here).
In the past, I have had a tendency to fixate on difficult or complicated parts of knitting patterns. Like crossword, jigsaw, and number puzzles, knitting patterns comprise a variable amount of predictability that becomes clear over time. The more one knits, the more salient the patterns-within-patterns become. In order to realize some of this predictability, I established a process of tinking - or unknitting - stitches and rows of patterns that puzzled me.
My experience with the garter tab cast-on functions as another example of how this make-unmake-remake process functions in my greater understanding of knitting. I carried my yarn to coffee meetings and across state lines, knitting and unknitting the garter tab cast-on, with intentions to demystify how it works.
The garter tab cast-on creates a square or rectangular piece of garter stitches - a 'tab' - through the rotation of stitches on the knitting needles. To begin, cast three stitches onto the needles. This is the provisional cast-on. Then rotate the stitches 90 degrees and knit into the stitches that are already alive on the needles. Knit the same number of stitches (3) for six rows, making a series of garter stitches.
At the seventh row, knit three garter stitches and rotate the stitches to set up the next motion. Insert the left needle into three of the stitches from the previous row. Put the stitches on the left needle and knit them. (If this is all sounding a bit complex, I understand. These types of techniques highlight the invaluable difference it makes to learn to knit with others or face-to-face with an instructor, as book and written instruction cannot provide the three-dimensional set of observations that are really needed to learn.)
Now this is where the garter tab cast on gets tricky. After knitting three stitches, there are still three stitches remaining from the provisional cast-on. Slide those three stitches, unknitted, onto the left needle.