What is a French Fly in Men’s Pants?

Maybe you’ve heard people tell you, “your fly is open,” and you thought to yourself, “what on earth is a fly?

Oftentimes, people think that a fly is the zipper of pants, but it’s not. If you’re wearing a pair of pants right now, you can sneak a peek at your fly. Now, if you see the flap covering the zipper – and that’s it, that’s the fly.

And if you want to know more about what French fly is, you’ve landed on the right website. Read on and discover more things about pants fly.

What is a French Fly, really?

The French fly (not French fry, although it sounds like) is an extra hidden closure for trousers that is attached to an internal belt or waist stay with an inside button tab. Its purpose is to relieve any tension on the top of the zip. It also allows the flap of the fly to sit down smooth and flat in a more relaxed manner.

What Goes with Navy Blue Shorts?

The French fly is most commonly seen on high-end dress pants and trousers. An outside button or a flat-hook closure can be used on the top of the pants. Intriguingly, the term “fly” appears to be confined solely to the opening of men’s trousers. Although, very seldom, to women’s trousers, too.

Sewing the Fly: How to Do It Professionally

As someone who owns trousers and pants with French fly, it is only necessary to know how to sew them, just in case. Of course, you can always visit the tailor if you want to. But isn’t it nice to have basic knowledge on how to sew it? We know you want to know, so we’ve got you covered. Below are the steps on how to sew a French fly.

Cut the Zip Placket

Firstly, cut two parts for the zip placket. The one part should be long enough for the zip and seam allowances and the other with iron-on interfacing.

Construct the Zip Placket

Like a regular zip placket, please measure the zip’s length. Then sew the placket pieces together to make it the correct size. The “nose” on the placket is what makes the difference. When the zipper pull is closed, the point of the nose must be at the same level as the zip pull. Turn the placket out, sew the long raw edges together, and sew a buttonhole in the size that best suits your needs.

Insert the Zip Placket and Attach the Waistband

After you’ve completed the first two steps, you’ll need to insert the zip placket and the zip, just like a regular zip placket. Finally, as before, sew the interfaced half of the waistband to the garment’s top edge.

Create the Waist-Stay

To create the waist-stay, cut two long pieces of durable woven fabric lengthwise on the grain. Every part should be long enough to go around half your waist plus a little extra, and the width should be double the finished waist-stay width plus twice seam allowances.
Fold all other pieces lengthwise, right sides together, stitch one of the short ends together, move right side out, and press. Then fold the entire length lengthwise.

Now it’s time to turn in the waistband facing and secure it in place to place each belt in its proper location, with the stitched closed bit in the front and the long-folded edge down. The left front should be just over the placket’s stitching line, and the right front must be midway over the zip tape. Pin them to the facing to indicate where they should go.

Stitch Belts to Waistband

After that, stitch the belts to the waistband facing, making sure the straps’ front edges are precisely where you pinned them. Stitch down to about 5cm from the center back seam, allowing for final waistband fitting.

Back Seam

Complete the final waistband fitting and the waistband center back by stitching. After that, fit the belt to your measurements and knit the two with each other at the center back seam. Fold the center back of the belt in half lengthwise and press, then stitch the remainder into place on the waistband facing once stitched together at the center back.

Opening and Completing Edges of Waistband

Like a regular waistband, fold the band facing the right sides together and stitch the front edges. Turn the waistband right side out and trim the sides.

Then fold the waistband facing seam allowance and the belt seam allowance in and under each other, and pin in place. Finish the waistband by basting and stitching in the ditch all the way around. Stitch the left front down firmly along the same stitching as the placket/zip stitching to secure the belt.

Attaching the Button

Finally, try on the trousers/shorts to assess where the belt button should go and secure it with a stitch. It should be positioned so that the front fly flap and zip are perfectly eased and closed.

There should be no stuffing together at the top of the zip, which indicates the belt is too tight. And there should be no strain on the zip, which means the belt is too loose.

Now that you know how to sew a French fly, you will be able to fix your fly next time.

The Bottom Line

At the beginning of this article, a French fly, also known as a waist stay, is an extra hidden closure with an inside button attached to an interior belt. It can be found on both men’s and women’s pants, though men’s pants are more common.

You may consider making a sample to test the directions when you first start making fly-front zippers. Make two or three pairs of pants with fly zippers in a row if possible. That way, the steps will become second nature to you, making it easier to insert these zippers in your future “I need to go to the tailor now” situations – if you understand what I mean.

READ ALSO: Advantages of Briefs Over Boxers

Jonathan B. Delfs

I love to write about men's lifestyle and fashion. Unique tips and inspiration for daily outfits and other occasions are what we like to give you at MensVenture.com. Do you have any notes or feedback, please write to me directly: [email protected]

Recent Posts