Sewing Tutorial | Inserting a Fly Front Zipper

I used to hate HATE inserting flies until I figured out this awesome method. It’s nothing groundbreaking but I feel like every time I opened a new book or pattern they would give me a slightly different variation on how to insert a fly. These are my 7 steps to inserting a fly that works and looks great every single time, no more dreading this process.

You may recognize that this is a repost of part of my Maritime Shorts sewing instructions. I figured it would be useful in a singular post for a few reasons. One, for people who need to insert a fly and aren’t making the Maritime Shorts, now you don’t have to wade through 30 some odd instructions just to insert a fly in something completely unrelated. Two, as I release more patterns with flies it would make me SO happy to have a tutorial to refer to for that step instead of doing the same photos over and over and over. So without further ado, here is the tutorial for Inserting a Fly Front Zipper (after the jump).

Step 1 | First prepare your Fly Facing and Fly Shield by fusing your interfacing to the wrong side of each piece according to the instructions that came with your fusible. You can optionally serge or zig zag stitch around the curved edge of the Fly Facing. For the fly facing you can do one of two things. Fold the Fly Shield in half with wrong sides together, sew around the side and bottom edges and either serge or zig zag stitch around the edges OR you can fold the Fly Shield in half with right sides together, stitch around the side and bottom edges and flip right side out so the seams are concealed inside of the Fly Shield.

Step 2 | Place Fly Facing on Left Front edge and stitch from top to start of crotch seam. Grade the seam allowance, press Fly Facing away from garment and understitch.

Step 3 | Place closed zipper face down along the edge of the Fly Facing making sure that the zipper stop is ¾” from the bottom edge of the facing. Using a zipper foot, baste along the right edge of the zipper with bottom edge of zipper turned up. This will keep this side of the zipper from becoming caught when you topstitch the Fly Facing curve. Sew the left side of the zipper to the Fly Facing both along the coil and along the edge of the tape.

Step 4 | Turn Fly Facing to inside along the seamline and press. Baste along the curved edge of the Fly Facing about ¼” in from the edge, this is the line you will follow to topstitch the fly curve. Turn shorts right side out and topstitch along your basted line going from bottom to top. Remove basting threads.

Step 5 | Now to attach the right side of the zipper. Fold the right side of the shorts under ¼”, pin and baste to zipper. Close zipper to be sure that it is positioned correctly and evenly and that the tops of your shorts meet.

Step 6 | With the zipper closed position the Fly Shield from the inside of the shorts aligning the folded edge with the topstitching of the Fly Facing. Pin in place and flip garment to the right side. Baste along the zipper through all layers. Remove pins, open zipper and stitch along the zipper.

Step 7 | Place a bar tack across the bottom of the fly catching both the Fly Facing and Fly Shield. With the zipper open stitch across each side of the zipper tape. Trim the excess zipper tape even with the top of the shorts. Do not cut the zipper tapes without first stitching across the zipper tape!

That’s it, that wasn’t so bad, was it. Pretty easy actually! Now you’ll have to find something else to dread sewing. As always, if you have any questions you can post a comment below or send me an email.

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57 Responses to Sewing Tutorial | Inserting a Fly Front Zipper

  1. I have just made my first ever fly. Next time, I’ll have to try your instructions!

  2. yesilikethat says:

    Yes! Thank you for this tutorial! I remember googling this a few years ago when I was making my first pair of trousers and there was nothing useful out there, except for a few mysterious diagrams and some cryptic instructions. Can’t wait to make the Moss skirt now.

  3. Barbara J says:

    I just completed a fly zipper using your tutorial. The only difference is I placed the fly facing on the right since it is a ladies capris … mine 🙂 But I suppose that is no big deal. Thanks again.

    • I suppose I should specify in the tutorial that this is for a US jeans style fly, the fly facing is on the left here for ladies pants, and I think from your email address you may be in another country? Glad you found the tutorial helpful other than that!

  4. This is awesome, I love you, thank you for sharing, may gold coins fall out the sky into your treasure chest/ bank account/ similar. I think I got it. Will try it for realisies once the heat has died down a bit XD

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  6. JLM says:

    Thank you for these instructions. They are the best I ever seen. Made a very difficult procedure easy!!

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  8. Jossie says:

    Anyone know what to do when the pants are being lined? I’m stumped! Thanks for any help at all!

  9. Kel says:

    I now officially hate zippers. Although this tutorial is great, it seems to be different to the instructions in the maritime shorts pattern. Running from the computer to the sewing machine every 2 minutes to check how to do it, and alternatively reading the pattern instructions as well made me stuff it up about a bazillion times. When I finally got it figured out and sewn in, I’d somehow managed to put the zipper in inside out… DOH! Next time, I will put my computer next to my sewing machine and follow only this tutorial. Ohwell, at least I’m now well skilled in unpicking.

    • Hmm, the tutorial and the instructions in the Maritime pattern are actually identical, in fact I copied and pasted the text from the pattern instructions straight into the blog post. I just double checked and they’re exactly the same, the only difference is the illustrations vs. photographs.

      • Kel says:

        Oh man I am the biggest idiot in the world. I do apologise! Next time I should read the step numbers. I was reading across the page instead of down the page meaning I was going from step 10, to step 12, then step 11… no wonder I was having such difficulties! I will not give up on my zipper, but I think I’ve unpicked it so many times now that I’ve started to ruin the fabric 🙁 Otherwise, I love my maritime shorts.

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  11. Beth says:

    Thank you for the great explanation! I finished my first moss skirt today and I love it! Great pattern 🙂

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  14. Leonie says:

    Thank you for this tutorial! I’m masking the Moss Mini skirt right now and I can not get my Head around step 5 (or step 14 in the pattern). Didn’t I just sew the zipper on both sides to the fly? How am I able to Open the zipper? Mine is sewn flat to the fly, which is sewn to the left skirt front.
    I Hope You can help me, thank you very much!

  15. Stephanie says:

    This version works for me. I like my zipper offset, and this process is getting printed out and posted up in my workshop. Thanks!

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  17. velosewer says:

    I have now followed your instructions and I can gladly say, your instructions worked. So now I know. And the zipper looks straight too.
    I used to follow another method but the top was always skewed for some reason. This method is dead straight and even:))
    Thanks Jen.

  18. Masha says:

    I think I am missing something. I followed the alternate instructions for the fly shield – I folded it right-sides-together, stitched around, then turned right-side-out. But now my fly shield is smaller than the one in your photos (which was just stitched and serged, not flipped), so when I position it with the folded edge aligned with the topstitching of the fly facing, it doesn’t cover the zipper. What am I missing?

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  21. Hanna Geshelin says:

    After an hour, having basted and removed zipper four times, I’m moving to a different tutorial. I thought the instructions were clear, but after struggling for all thsi time I realize that can’t make sense of the photos, they seem to contradict each other. Don’t have a clue why everyone else finds these easy or what I’m doing wrong.

    • Jen says:

      Hi Hannah- If you let me know what you’re having trouble with I’d be more than happy to help but without more info on what’s going wrong I can’t do much. Different methods work for different people and perhaps this just isn’t your method.

      • Thanks, but a lot of time has passed and I don’t remember what my issues were. 🙁 I found another tutorial that worked for me. As you suggested, different strokes for different folks.

  22. Hannah says:

    That was an amazing tutorial!!!! thank you so much!
    I was struggling with how the pattern said to put them in, but now i get it. I will be bookmarking this for future reference 😛

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  30. deborah cajegas says:

    thank you soooo much of your tutorial. I’ve been looking quite sometimes how to attach zipper on trousers in different tutorial way but quite hard for me to understand as a beginners.
    but i found yours very clear and easy to follow.
    thank you once again for sharing to public.
    i did mine and it perfectly works well.
    thank you! you deserved 5 stars from me.
    good luck and share more.
    God bless!!!!

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  35. Janet says:

    Thank you so much for this, Jen. I’m new to this and was struggling a bit with the instructions for the Moss skirt but this makes it so much clearer. One question about step 2: “press Fly Facing away from garment and under stitch.” I thought I was doing it right (under stitching the clipped SA to the fly facing) but for the life of me I can’t see the under stitching on any of your pictures so am wondering if I’m doing it wrong? Also, thanks for explaining that the fly is the opposite side in the US – I was looking at Tasha’s instructions in the Sewtionary and was panicking because her instructions say to put the fly facing on the right side while yours say left side. Now I understand 🙂

  36. Janet says:

    I’m with Leonie – I have completely lost the plot at step 5. Shouldn’t I unbaste the side of the zip closest to the centre front? Otherwise I just can’t see how that side can then be attached to the other side of the skirt as it’s already basted to the fly facing.

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  40. Denise says:

    Oh thank you! I had learned and forgotten the 1cm off-set. I was working on a pair of rub-off jeans, and the zipper I did was bothering me as it was so close to the finished edge. While pinning the waistband, I decided to google search, and ta-da! So thank you for saving my first rub-off from the wadder pile 🙂

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  42. Katharine says:

    Thank you for this! I’m making a pair of Ottobre pants & could not fathom the instructions for the life of me. I now have a very nicely installed zipper thanks to this excellent tutorial!

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  44. Mazza says:

    I followed your instructions step by step. Very clear and easy to follow! I also had a pair of jeans handy to copy just to check my understanding of all the bits! Thank you so much.

  45. Ann says:

    This was so helpful and easy to follow! Thank you- !

  46. joann eidhoff says:

    A terrific save for me. I usually do Sandra Bettina’s excellent zipper application, but this time I forgot to add the addition seam allowance at the front center. With just a normal seam allowance I was up a creek with no paddle. Then I found your terrific tutorial and have saved my trousers. I think your application will replace my former one. Thanks for the save.

  47. Hmmm… I can’t see where the basting is in step 6. I’m guessing “all the layers” doesn’t mean both the left front/facing and the shield? I was a little confused earlier, but I followed your instructions and didnt overthink it and it seems to be going well so far!

  48. Alice Hiller says:

    Hi Jen, I believe there is an error in the Maritime shorts pattern, I was confused until looking at this great tutorial. Step 16 in the pattern says to align the “serged” edge with the topstitching of the fly facing and your tutorial shows it should be the “folded” edge that is lined up with the topstitching.

    • Jen says:

      Hi Alice- Did you purchase your pattern a while ago? This is something we caught when going to print. Let me know – you can email us at and I can help you determine that if you need.

      • Alice Hiller says:

        Hi Jen, actually it was the pdf version I bought from your website this May. I bought the Moss skirt pdf too, it has the same error. No worries, I figured it out, just wanted you to know! Thanks, i love my shorts, hope to have time make the skirt soon.

  49. Erin Howe says:

    I was following so carefully until step 5. The pin to the zipper and baste lost me.

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