Buttonhole Stitch

Common. Buttonhole Stitch, as the name implies, was meant to reinforce the slash made to create the buttonhole. The same method of stitching as for Blanket Stitch, but the vertical threads are stitched close together.

Mary Thomas's Dictionary of Embroidery Stitches, p 17 [Button Stitch, Buttonhole Stitch*] The Stitches of Creative Embroidery, p 97