Couching is simply sewing a heavy thread in place with a finer thread. Its a retro technique, too, that was originally done by hand, but it works beautifully by machine as well. I use a zigzag stitch to secure the heavy thread in place.
The top of a tank top and the bottom of a large men's shirt - a one of a kind dress! Perfect idea for yardsales where all the nice men's dress shirts are XXL. Great for maternity dress too. Id use it for a nightgown!