Hand overcasting is a couture stitch that is rarely used today. However, Susan Khalje, a Threads contributing editor and couture expert, would argue that it’s as essential in the 21st century as it was hundreds of years ago.

Susan points out that a hand-finished raw edge, in place of a serged, pinked, zigzagged, bound, or machine-sewn finish, is lighter and more supple. It’s also less visible, making it appropriate for delicate garments such as the armhole seam allowances on a lace blouse.

For the softest, least bulky finish, Susan recommends using a high-quality, smooth thread, such as Mettler silk-finish cotton, or other mercerized sewing thread. Work with a single strand of thread, and don’t wax it. Beeswax is used to strengthen thread for applications such as seaming or attaching buttons; it’s not needed for an overcast edge finish.

Overcasting is done with a whipstitch. Susan demonstrates…