Under stitching is done on the right side of the facing very close to the seam. It holds the facing and the seam in place
After attaching the facing to a curved edge seam is clipped at intervals before turning the facing towards wrong side .By doing so curved seam will lie flat when the facing is turned inside. This gives good finish to the garment.
Easing is done while joining two cloth pieces in such cases where one of which must be longer than the other to get good finish. While attaching bias strip to a curved edge easing is done.