This stitch is the Siennese Stitch. This is the latest stitch from my 100 Stitches list.
For my stitch demonstration, I am using perle cotton floss. This is DMC Color Variations #4022. I set up two parallel guidelines so that I could keep my stitch size consistent.
The first step is to come up through the fabric and form a Straight Stitch.
When finished, secure your floss on the underside of the fabric. Here is a look at the underside of this stitch: