With a tapestry needle, bring the yarn from the back to the front of the fabric at the base of the stitch that is to be duplicated. Insert the tapestry needle from right to left behind both sides of the stitch above the one being duplicated. Complete the stitch by inserting the needle into point at which the yarn first came through to the front and pull it back to the wrong side. Repeat as necessary to work additional duplicate stitches in desired locations.
Duplicate Stitch
Duplicate Stitch