Flat Felled and French Seam

French Seam.The French seam is strong and durable. Because the raw edges of this seam are completely enclosed, there is no need for an additional seam finish. This seam is usually used on lightweight woven, sheer, and other delicate fabrics. French seams may be constructed by hand or sewing machine.
Steps:

Place the wrong sides of the fabric together.
Stitch 3/8 inch from the cut edge of the fabric. Press.
Trim to within ⅛ to 1/4 to inch of the stitching. Press seam open.
Fold fabric over at the seam,right sides together, covering the cut edges. Press again.
Stitch on seam line, approximately 1/4 inch from the folded edge, to enclose the raw edges.
Press flat and then to one side. Easily done on straight edges, the French seam can also be used on curved edges. The enclosed edges may need to be clipped before pressing in Step 3.

Flat-Fell or Flat-felled.
This seam is designed for woven fabrics and straight edges....