Understitching

Understitching is a sewing technique used to keep facings or linings in place and prevent them from rolling to the outside of a garment. By sewing the seam allowance to the facing close to the seam line, the edge stays flat and neat, improving the garment’s finish and drape.

The basic method involves sewing a line of stitches along the edge of the facing, typically about 1/8 inch (roughly 3 mm) from the seam line. Before stitching, the seam allowance is pressed toward the facing. With the facing turned to the inside, the stitch line catches the seam allowance and the facing but not the exterior fabric, securing the facing to the garment. The stitch is usually a straight machine stitch, though fine hand stitches can be used for delicate fabrics.

Understitching is commonly used around necklines, armholes, waistlines, collars, and hems where a facing is employed. It helps the facing stay hidden and prevents unsightly roll or edge exposure. The technique also reduces bulk at the seam and contributes to a cleaner, more professional finish.

Considerations include fabric type and weight; very slippery or thick fabrics may require adjustments in seam allowance width or stitch length. Understitching is generally avoided on hems that are meant to roll slightly for drape, or on edges where the facing should float freely. It is often one of several finishing steps used to create durable, well-constructed garments.