Sometimes it is necessary to secure two pieces of fabric together without wanting to show the stitching; for example, to attach a neck facing to the bodice of a garment without top-stitching all the way around the neckline (or to secure a lining to a skirt at certain points). You can sew an invisible stitch line by "Stitching-In-The-Ditch". This simply means you sew the two pieces together over top of an existing seam line. To attach a neck facing (once turned to the inside) you might "stitch-in-the-ditch" at the shoulder seams. To secure a lining to a skirt and prevent it moving, you might "stitch-in-the-ditch" along the existing dart lines.
1. Pin the 2 pieces of fabric together so that they sit nicely.
2. On the right side of the garment, stitch slowly and carefully along the existing seam line being sure to secure your stitching at the start and end with a 3 stich forward-back-forward motion.
3. Your fabric pieces will how be held in place and your stitching "invisible".