I totally made up the name of this stitch. If anyone out there knows it's "proper" name please let me know! This is a really unexpected stitch. I love it's uneven quality and it's so quick you could use it to go all around the border of something big, like a sheet or a baby blanket.
Start with a vertical row of horizontal stitches and then introduce the second thread color at the bottom of the row in the middle.
Wrap the second color of thread as shown above all the way up the horizontal stitches.