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I’ve noticed during the testing of my new PDF sewing pattern (Justin Pants, drop crotch styled, coming on One thimble issue 14) that many intermediate sewers still don’t know how to properly understitch a seam and why they should never skip this step.

So: what’s better than a video tutorial? I will show you how to construct a lined hip patch pocket, including a row of understitching right along the hand opening of the pocket (scroll down to find the video… and follow me on my new YouTube Channel <3).

But, first, just a couple of words about understitching, for who needs to know more about this technique.

What is understitching used to?

Understitching is basically a construction seam, supposed to stay hidden inside your garment. You should sew it using a regular straight stitch, short-medium length (2-3).

The idea is to prevent linings and facings showing on the outside of your garment, keeping the seam rolled toward the inside of the garment and the edges crisp and sharp.

 Serger Pepper - Understitching & sewing a lined hip patch pocket - the seam

How do understitching works?

By stitching the seam allowances to the lining (or facing) layer they will keep it hidden inside, while no seams will show on the outside (unlike a topstitching).

It is used at necklines, armholes, waistlines, pockets and it is often included in pattern instructions.

If you are sewing a garment including one of these details and it doesn’t tell you to understitch it, my suggestion is: add this step, right after sewing the main seam.

7 tips for perfect understitching

  • Seems obvious but: never ever skip it!
  • Always trim (and grade, with heavyweight fabrics) your seam allowances before you understitch, clipping them on concave curves.
  • Use a thread color similar to the lining/facing, so it will disappear!
  • Sew the understitching seam as close to the main seam as you can (the ideal distance is 1/8″ or less).
  • Gently stretch the main seam open, by pulling fabric on both sides (left-right, not front-back!), while it is under the presser foot.
  • Sewing a precious garment? Understitch it by hand, for a couture detail!
  • Need to understitch on corners, hard to reach? Go as far as you can or do it by hand!

Let’s see the understitching technique in action… and learn how to sew a lined hip patch pocket!