Work the stitch from left to right, along two lines parallel to the seam. Come up at the baseline, take a long diagonal stitch to the right and insert the needle in the upper baseline. Do a small back stitch to the left along this baseline, then take a long right diagonal stitch down to the lower baseline. Keep working in this manner across the length of your seam.
Play around with the lengths of your stitches and where you position them along the seam. This stitch is easy to combine with others for some special effects.