Interfacing

Interfacing is a common term for a variety of materials used on the unseen or "wrong" side of fabrics in sewing. Interfacings can be used to stiffen or add body to fabric, such as the interfacing used in shirt collars; to strengthen a certain area of the fabric, for instance where buttonholes will be sewn; or to keep fabrics, particularly knit fabrics, from stretching out of shape. Interfacings come in a variety of weights and stiffnesses to suit different purposes. Most modern interfacings are made to be ironed in place, though some must still be sewn by hand or machine.