Understitching is a technique used to secure the seam allowance to the fabric on one side of a seam (usually a facing or lining). It makes it easier to press that side to the inside of the garment and creates more of a pull on the facing or lining so it is less likely to show from the right side of the garment.
- Prepare your main fabric and lining pieces, ready to sew the seam. Here, my main fabric is a plain green cotton and the lining is a floral viscose.
Sew the seam with the fabrics right sides together.
- Press the seam allowances towards the lining. Here’s what my sample looks like from the right side…
…and from the wrong side:
From the right side, stitch down the edge of the lining at about 1/8″ from the edge of the seam. You can use an edge-stitching or stitch-in-the-ditch foot for this, but I find it quicker to just set my machine’s sewing needle position as far to the left as it can go, and then line the seam line up to the left edge of the presser foot.
Here’s what it’ll look like from the right side..
(I’ve used a contrasting thread here so that you can see the stitching more clearly, but if you’ve used a matching thread, the under stitching should be pretty subtle.)
Press the lining to the inside of the garment. You should find that the understitching helps the lining to lay nicely to the inside. From the wrong side, you’ll see a tiny strip of the main fabric:
And from the right side, you won’t see the lining peeking out at all:
And that’s all there is to it!
Now, depending on the sort of seam you’re stitching, you might not be able to understitch all the way from edge to edge. With armscyes (armholes) and some necklines, just stitch as far as you can and focus on the curved sections where the facing or lining is most likely to peek out.