What is a French Fly in Men’s Pants?

Last Updated: July 7, 2022

A common misconception about pants is that the fly is the zipper, when the fly actually describes the flap of material that covers the zipper. The fly lies over the zipper to create a more streamlined look and to protect the zipper from getting caught on anything.

A French fly is an additional fastening inside the waistband that holds the fly material in place. It covers the zipper and is attached at the top with a button or hook and eye. A French fly also takes some of the strain off the zipper, helping the pants to fit better and creating a more relaxed look.

french fly closure on pants

In this article I’m going to cover everything you need to know about the French fly so you can look stylish, streamlined, and fashion-savvy.

What is a French Fly on Pants?

A French fly is an extra button inside the waistband of your pants. It secures the fly material and prevents it opening or flapping around. Have you ever seen pants with a zipper and fly, but the fly is gaping open to expose the zipper? Well, that’s a problem solved by the addition of a French fly.

The French fly also serves to alleviate some of the strain from the zipper. Having a straining zipper isn’t a good look so the French fly both covers up the zipper and takes some of the pressure away from it by providing an additional attachment point in the waistband.

French flies are usually seen on more formal clothing, like suit pants, and occasionally on women’s pants. It might be a traditional flat button and hole, a snap button, or a hook and eye fastening.

Why is a Men’s Pants Zipper Called a Fly?

Remember that fly doesn’t refer to the zipper, but rather the flap of material that covers the zipper. In Old English, the word fly was used to describe any piece of fabric attached by one end. Like a flag on a pole or a banner hanging from a wall.

For this reason, tailors began to call the zipper-covering flap a fly too. It makes sense, it’s a piece of material that attaches on one side and is loose on the other side. The fly in men’s pants attaches at the side but is open across the zipper.

Despite similar tailoring existing in women’s clothing, it’s unusual to hear this flap of material being called a fly when it appears on women’s pants.

French Fly Pattern

You never know when a tailoring emergency may rear its head. So here’s a quick guide on sewing patterns for a French fly.

  • Cut your zipper placket – The placket is the opening of the pants, your zipper will lie along the placket. Cut your zip placket from two pieces of fabric, applying iron-on interfacing to one piece.
  • Sew the two placket pieces together, finish the raw edges, and add a buttonhole – Make sure the finished placket is the correct length for the zipper and the buttonhole will fit your button of choice.
  • Insert and attach the zipper placket into the open waistband of the trousers.
  • Cut two long pieces of sturdy fabric to make the waist stay. These each need to be long enough to wrap halfway around the waist. Fold the pieces lengthwise and stitch the ends to secure them. Line the waist stays along the inside of the pants waistline so the ends are over the edge of the zipper placket on one side, and the zipper tape on the other.
  • Stitch the waist stays securely to the waistband and fold the waistband seam over the waist stays. Stitch the seam down to secure the two together.
  • Try on the pants to check there is no bunching along the waistline. If all seems well then attach the button, taking care to align it properly with the buttonhole of the French fly.

What is a French Bearer?

A French bearer is the name of the button, snap button, or hook that attaches the fly to the internal waistband of a French fly. This one’s easy to remember, the French bearer literally bears some of the strain in the zipper and waistband.

What is the Purpose of a Waist Stay?

A waist stay is an additional piece of reinforced fabric that runs along the inside of the waistband in a pair of pants. It’s where the French bearer is attached and works to secure the French fly material.

Waist stays also help with reliving some of the strain through the zipper and waistband so the pants lie more flat in the front.

Final Thoughts

So, a French fly in men’s pants is an extra fastening hidden in the waistband of your pants to secure the fly material and streamline the waistline.

The next time someone says, “hey your fly is open!” you’ll be able to correct them if they actually mean the zipper!