Thread a tapestry needle and bring yarn up through desired stitch; now *go across to knot on opposite side and come up under lower bar of knot which looks like a “u”, cross and go under curve of the top of the stitch which looks like an inverted “u”. Repeat from *.
See also: Mattress Stitch, backstitch, whip stitch, seam – rows to stitches, Kitchener Stitch – Grafting Knitting, garter seam, flat seam, baste, sew snap tape to front bands, sew snap tape