Very similar to the overhand stitch. Use it to secure hems or other projects requiring a strong invisible seam. The only difference is it create a straight stitch across the seam and not a slanting one.
Work right to left, keeping stitches close together. Place the folded and pressed seam-lines to be joined together. Pick up a couple of threads from the top fabric taking the needle in on a diagonal to the edge, then a couple of threads from the adjoining fabric.