Paragraph 122. The double featherstitch is started in the same manner as the single featherstitch (Paragraph 121) except that instead of crossing to the opposite side of the central line after completing one stitch, two parallel stitches, exactly the same length, are taken on each side of the central line before crossing.
Study the position of the needle shown in Figure 21. Note that one of the small stitches has been completed just as in the single featherstitch, and that the needle is inserted and the thread is lying in the loop under the point of the needle for the second stitch. When this stitch is finished, the next stitch will be taken as shown in Figure 22; it will be followed by a second stitch parallel to it, completing the two on that side. Continue the process.
Double featherstitching may be used anywhere that single featherstitching would be appropriate.