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How (+ Why!) to Use Understitching for a Professional Finish

The secret to a polished, professional finish on all your garments? It’s understitching. This sewing technique keeps the facing from rolling outside of the garment and helps you to press a crisp edge along necklines or anywhere the garment is faced.

Why bother understitching?

The understitching helps the edge roll every so slightly inward, keeping the facing edge smooth and unseen.

Plus, it’s easier to press the facing inside if it has been understitched. While it might seem like an extra step in your garment construction, it actually make turning and pressing easier. 

example of with and without under stitching

The difference can be subtle, but it does make your garments look more professional. For example, compared to the understitched sample above, the edge without understitching is not as smooth, the fold is not as neat and even. The understitched facing folds over more precisely and is flatter.

Where to use understitching

A great spot to use under stitching is on a sleeveless dress or top. Whether it’s a one-piece facing that encompasses both the neckline and the armholes or separate facings for both, understitching keeps the facing edges looking sharp.

Ready to understitch your facings? Here’s a step-by-step tutorial.

Step 1: Prepare the facings

prepare facings

Prepare the facings as the pattern instructs. Add the required  interfacings, either to the garment edge or to the actual facing, and finish the facing edges. In the example above, I have a blouse back and the matching facing — in a real garment, it would be some type of complete neckline with shoulder seams. 

Step 2: Stitch, clip and trim

stitch on facing then clip and trim

Sew the facings onto the garment edge, and then clip to the stitching as needed. Curved edges need clipping so that the fabric in the seam allowance can spread when turned inside the curve.

If your seam is curved in the other direction, then you may need to clip and remove some fabric by cutting small notches.

It depends on the fabric, but I generally also trim the seam allowance down to about ¼” to create less bulk at the edge.

Step 3: Press the facing

press facing toward seam allowance

Once you’ve clipped and trimmed the seam allowance, press the facing away from the garment, along with the trimmed seam allowance. At this point, don’t flip the facing to the inside — you want a smooth area where the seam is stitched. 

This is how the inside looks, with the facing and the seam allowance flat and pressed away from the body of the garment:

facing pressed away inside the garment

Step 5: Understitching

stitch along facing edge

Now for the actual under stitching!

Stitch along the facing, very close to the actual seam. Make sure the seam allowance that’s on the underside is caught in this stitching. Depending on your fabric thickness, you can be very close to the actual seam, or up to about 1/8″ away for more bulky fabrics.

Typically this stitching is done in a matching thread so that it is almost invisible. Here I am using white thread to make it easier to see.

Step 6: Press the facing to the inside

press facing after understitching

Turn the facing inside the garment and press to create a crisp edge.



Lugene Fernald

So true! I think this skill is the ONE thing that took my garment making from looking homemade to “made with excellence.” Only one thing I would add that would make that seam even better is grading the seams. Instead of trimming both seams the same length, trim both seam allowances to 1/4″, then trim the seam allowance that lies against the FACING to 1/8″. Using applique scissors helps to keep from cutting both seam allowances again when you are trimming the facing side of the seam allowance further. Then clip and understitch. Though it goes against MY common sense, the rule is that “the longer seam allowance goes against the public side of the garment.” Plus you’ll find out very quickly if you don’t trim them that way, then it’s very hard to catch the short seam allowance with the understitching. It is a bit tedious, but it removes a lot of bulk that allows the fold to lie even flatter.


Thanks Lugene, for reminding of this one where we grade the seam allowances and the one clsoest to public side should be longer as it prevents the smaller one showing through. I’ve totally forgot about this one.

Alicia Fleming

Very helpful information to make garments look professional.

Nancy Werner

Thanks for the excellent tutorial. Now, pray for me!

Robin Jones

Just curious…why not just sew close (say, 3/8) from the start to avoid so much trimming and waste of material? This makes sense to me, but I’m learning and know there has to be good reasoning for doing this many steps.

Emma M Heap

I’m guessing the pattern will be designed for that seam allowance, so if you sew closer, the size will be out?


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