I am teaching myself how to quilt. I am learning alot on this site. As an alternative to sitd, which is the only thing I know how to do, some of you advise to use a serpentine or zigzag stitch. Does this go over both sides of the seam? In other words, do you stitch down the center of the seam so that you are sewing on one layer of fabric on one side and three layers on the other side where you have pressed the seam allowances? Am I making myself clear? Thanks.