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Understitching: How to Create a Sharp, Seamed Edge

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If you are new to sewing, some of the terminology can be confusing. Doesn't "bolt" mean to run away? Cutting something on the "bias" just sounds offensive. And, "feed dogs" seems more like a command than a sewing machine part. Trying to understand exactly what the various terms mean, how they work, and especially when to use them may seem daunting. But, as you learn each one, they'll become commonplace, and soon "nap" will mean more than dropping off for a little snooze. Today, we meet: understitching, which is not a seam done in a sneaky or under-handed manner and/or by Underdog. Read on to find out what it really is.

By definition, understitching is a line of straight stitching sewn just beyond the seam line of two pieces that have been sewn together to create a seam along an edge. One of the pieces is the outside of your project, the other is the inside. In order to keep the seamed edge sharp and clean, you understitch the inside piece to the seam allowance so it won't roll to the outside along the edge seam and look messy and unprofessional.

Understitching is referred to a lot in garment construction, especially around necklines with facings. For example, when a facing is sewn to the edge of a scooped neckline, you don't want to see the facing rolling out around the neckline when you wear the garment. You understitch the facing to the seam allowance so the facing stays in place. You might also see understitching around the waist of a lined skirt – the style without a waistband.

Although possibly more common in garments, we've found plenty of uses for understitching in home décor sewing. For example, on our Pleated Crib Skirt and our Tiger Eye Box Pleat Pillows, understitching helps keep the pleats knife sharp.

Next time you're out shopping for ready made items (a rare excursion for you since finding Sew4home, right?!), look at the inside to see how things are made. You'll notice how often understitching is used to create a professional finish.

How to Understitch

  1. As with the majority of our technique tutorials, we've used unusual fabric and thread combinations so you can clearly see how to execute this technique successfully. In this sample, we selected a light fabric for the inside and a dark fabric for the outside with a bright thread. In your projects, you would use the fabric of your choice (which may or may not be the same for the inside and outside pieces) and thread to coordinate with your selected fabric(s).
  2. If you're sewing a project with instructions provided, such as an off-the-rack pattern or following a downloaded tutorial, there are likely to be references to understitching where appropriate. If you're creating an original, you'll begin to quickly spot where you need to understitch because you'll get that "inside-rolling-to-the-outside" thing happening along a seamed edge. In our example, we will refer to the "inside" as a lining and the "outside" as the right side.
  3. Set up your sewing machine for regular sewing with a straight stitch.
  4. With right sides together and using the appropriate seam allowance, sew the right side piece to the lining piece. Remember, the dark fabric is our outside fabric and the light fabric is our lining.
  5. Grade (or trim) the seam allowance to eliminate excess bulk in the seam. This means you trim one seam allowance edge narrower than the other.
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  6. Press the graded seam allowance toward the lining.
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  7. Lay the sewn piece out flat, right side up. The lining piece should be to the right and the right side piece to the left. The seam allowance should also be laying to the right underneath the lining... since you just pressed it that way.
  8. Place this flat piece under the machine's presser foot. The seam line should be just to the left of the needle, approximately ⅛". You are preparing to stitch on the lining side.
    NOTE: We're using an open toe foot so you can see exactly where to stitch. You would use a standard presser foot on your machine.
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  9. Sew a straight line of stitching through the lining and the seam allowance underneath. This line of stitching should be as long as the edge seam you want to keep from rolling.
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  10. Fold the two pieces back together along seam line (ie. wrong sides together) and press for a sharp edge. Here it is from the back.
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  11. From the front, your seam edge should look straight and clean, just like the photo below. Can't see the lining, can you?
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  12. In case you're wondering what our sewn piece would look like without the necessary understitching... here's a second sample we made. It is identical is all ways except for the understitching. And there's that lining, rolling out into view where we don't want it. 
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Contributors

Sample Creation and Instructional Outline: Jodi Kelly

Section: 

Comments (10)

tenajl said:
tenajl's picture

I didn't understand the purpose of understitching.  Seemed like an extra step for no reason.  After reading this tutorial I will go back and understitch a couple of things!  Thank you.

Marie Z. Johansen said:
Marie Z. Johansen's picture

What a useful tutorial! I always wondered about this and now I know! Thanks. I have bookmarked this!

lawlzlaura said:
lawlzlaura's picture

I'm a total garment sewing newbie and I came across this post yesterday. I read it, and thought to bookmark it for future reference. You never know, maybe I'll have to use some understitching in the crazy distant future! I get home to continue working my snails pace on a jumper I was assembling and there it was, step number 7, understitching the lining on neckline! This tutorial couldn't have come at a better time. Thank you!!

Elizabeth said:
Elizabeth 's picture

Thank you for such a lovely and clear tutorial. It is an answero my problem. Brilliant !!!

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ Elizabeth - so glad to have solved a problem!

Luciaharrison@hotmail.com said:
Luciaharrison@hotmail.com's picture

Im New to Sew4Home. I was looking for ideas for for bed linnen when I can accross this site. I love it.

Ive decided to do oven mittens, pot holders, couple of tea towels as sets for each of my daughters and sisters as Christmas present. 

I have found beautiful ideas. I cant wait to start and to give them to my family. 

Your hard work is much appreciated.  Thank you

Nancyjc said:
Nancyjc's picture

As a self-taught sewist, I've never understood the value of understitching .... and my necklines never seem to turn out the way they should.  Now that I've learned the reason for doing this my necklines are looking perfect.  Your instructions and tutorials are so clear and really make sense of steps that I've never really understood.  Since I've been reading your tutorials and visiting your site daily, my sewing projects are turning out beautifully.  I wish Sew4home had been around when I was first starting out - you are absolutely invaluable - thanks so much!

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ Nancyjc - thanks for taking the time to post such a nice note. It's makes all the hard work worthwhile 

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