Secure the thread on the wrong side of the fabric and work from the top of the stitching line to the bottom. Bring the needle to the surface and take it to the right before pushing it back through the fabric. Bring it back up below and halfway between the first two needle positions. Pass the thread under the needle and pull through, catching the thread.
The next stitch is made by taking the needle down to the left and bringing the it up through the fabric halfway between the two needle positions. Pass the thread under the needle and pull through, catching the thread. Continue in this manner alternating the sides until the feathering is worked for the desired length.