Interfacing is used to add stiffness to fabric. On garments, patterns will typically call for interfacing in areas needing the extra body, like a shirt collar, or strength, like buttonholes. When sewing knit fabric, you may choose to use interfacing to keep the fabric from stretching out of shape.

When should you use interfacing?

Garment patterns typically call for interfacing on areas needing extra body (like a shirt collar) or strength (like buttonholes). If you are sewing knit fabric, you might use interfacing to keep the fabric from stretching out of shape. The pattern usually tells you what type of interfacing to buy and how much.

When should you not use interfacing?

It has an adhesive on one side which bonds permanently with the fabric when applied with an iron, due to the combination of heat and steam. Fusible interfacing is suitable for most uses, but avoid it for: very textured fabrics – the glue won't bond well to the fabric.