Understitching

Understitching is a row of stitching that joins the seam allowances of an enclosed seam to the facing or lining side only. It's sewn after the seam is stitched and before the facing is turned to the inside. Because the allowances are anchored to the facing, the seam naturally rolls toward the inside of the garment, so the facing, lining or under collar can't creep out to the right side.

It's invisible from the outside and takes a couple of minutes, and it's one of the techniques that most improves how home-sewn garments look.

Where to use it

• Facings at necklines, armholes and front openings. See Facing.
• Linings that finish an edge, such as a sleeveless bodice lined to the edge.
• Under collars and cuff facings. See Collar.
• Waistband facings and pocket linings, such as the lining of a slant pocket on trousers.

How to understitch

1. Sew the seam joining the garment and the facing, right sides together.
2. Trim, grade and clip the seam allowances, so they lie flat.
3. Press the allowances toward the facing.
4. From the right side of the facing, stitch through the facing and both seam allowances, about 1/8" (3 mm) from the seamline. The garment itself is not stitched.
5. Turn the facing to the inside and press, letting the seam roll very slightly to the inside.

Work slowly on curves, spreading the clipped allowances flat under the facing as you go, so they don't fold or bunch under the stitching.

Points and corners

You can't understitch right into a sharp point or corner, such as a collar point or the corner of a square neckline. Start and stop about 1" (2.5 cm) before the point, and rely on careful trimming and pressing for the last stretch.

By hand

For fine fabrics and couture finishes, understitching can be done by hand with a tiny prick stitch through the facing and allowances. It's less visible on the facing side and gives more control on delicate fabrics.

Understitching or topstitching?

Both hold a seam in place, but topstitching shows on the outside and is part of the design, while understitching is hidden on the inside. Use understitching when you want a clean edge with no visible stitching. See Topstitching.