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Tutorial: Mock Flat Fell Seams

Flat fell seams are used to strengthen garments and are often seen on heavy weight fabrics such as denim and canvas. Last week, we showed you how to do a traditional flat felled seam with a felling foot, and how to do it without a felling foot.

Now take a look at your jeans. From the right side it appears to be a regular flat fell seam. Look at the inside and you’ll see that instead of a traditional flat fell, it’s most likely a mock flat fell. The simple reason for this is because in production sewing it’s faster to make a mock flat fell seam. It also has the added benefit of making a seam that’s slightly less bulky, which is great for very heavy materials like denim.

This simple tutorial shows you how to apply a mock flat fell finish to your own sewing.

Tools Needed

  • fabric
  • scissors
  • pins

1. Finish the seam of one edge. Here the edge is serged, but pinking or zig zag stitches work as well. Be sure that the seam isn’t cut away when serging. If this is a concern, finish this edge after step #2.

2. Sew the seam using the required seam allowance.

3. Trim the unfinished seam to 1/4″ wide. There’s no need to finish this seam since it will be encased by the longer seam.

4. Press the seam allowance to one side. Make sure the seam is flat on the right side before continuing.

5. Pin the seam in place.

6. The final step is to stitch the seam down. The stitch should be parallel to the initial seam and about 3/8″ wide.

There you go! You can use this seam whenever you want a faster version of a flat fell, or if the traditional flat fell produces a bit too much bulk.

Caitlin Clark

Caitlin is the Colette Patterns design assistant. You can follow Caitlin at her blog, the story girl.



February 21, 2011 #

I’m thinking that this technique might be easier to do with very curved seams as well? After reading the tutorials for the other felling techniques I was trying to think about how you might finish a princess seam on a women’s shirt without burning your fingers off on the iron… I did a little retail snooping yesterday and found that a couple of the shirts I looked at had mock flat felled seams on the princess seams and proper flat felled seams on the side.


February 21, 2011 #

I just love your tutorials, Colette family, they are so clear with the photo essay and with these techniques, just long enough/short enough too!


February 21, 2011 #

I am thinking of trying to make jeans next week so this tutorial is great, wish me luck!


March 4, 2013 #

I really enjoy your tutorials. I have a question about the mock flat felled seam… For the last step, where you tack the serged seam down, you sewed on the “wrong” side of the material. Does this make a perfect seam on the “right” side? My machine would not – it would be obvious that I sewed on the “wrong” side. Does this matter?
Thank you for these tutes!


November 14, 2013 #

Simple explanations. Veryeasy to understand :) Thanks ::))