Strips of bias tape or seam binding are folded and sewn over the raw edge of the seam allowance.
Most fabrics. Ideal for items that will have visible seams.
Makes a neat, clean finish. Raw edges will not ravel because they are completely encased.
Adds some bulk to the seam allowance. Somewhat time consuming. Requires precise sewing.
How to Make
Press the seam allowance open. Take lightweight seam binding or double folded bias tape and fold it around the raw edge of the seam allowance placing the wider side underneath. Stitch close to the folded edge of the tape, sewing through both sides of the tape at once. Or you can use a narrow zigzag stitch to sew the tape in place.
Note: Remember to preshrink your seam binding or bias tape and check it for colorfastness.