Horizontal: Bring threaded needle out from back to front at base of knitted stitch to be covered. *Working right to left, pass needle in and out under the row above it and back into base of same stitch. Bring needle back out at the base of next stitch to the left. Repeat from *. Vertical: Beginning at lowest point, work as for horizontal duplicate stitch, ending by bringing the needle back out at base of stitch directly above stitch just worked.