Couching Stitch is made by stitching over a length of thread using small straight stitches.
Bring the thread up through the fabric and lay the length of thread down along the line of your design, you can remove the needle from this thread now. Using a second length of thread (can be contrasting) make a short straight stitch over the first thread, bring the needle up a short distance away and repeat the short straight stitch. Continue along the length of the thread leaving room to thread the needle with the couched thread again and take it through to the back to secure. Finish off the couching stitches and secure the couching thread at the back of your work as well.