The hole in men’s boxers is called a fly, and its primary purpose is to let you urinate without pulling your underwear down. The design dates back to the earliest commercial men’s underwear and has remained a standard feature for decades, though not every modern pair still includes one.
What the Fly Is Actually For
The fly is a practical opening in the front of the underwear that lets you pull your penis through the fabric rather than lowering your waistband. This is especially useful when you’re wearing a tucked-in shirt, a belt, or layers of clothing. Instead of undoing everything from the waist down, you can use the fly on both your underwear and your pants to handle things quickly.
Beyond bathroom convenience, the fly also helps preserve modesty in situations like crowded restrooms or outdoor settings where pulling your waistband down would mean more exposure than necessary.
How Different Fly Styles Work
Not all flies are built the same. The most common styles break down into a few categories.
- Vertical fly: Two overlapping pieces of fabric create a vertical opening in the front pouch area. This is the classic design found on traditional briefs and boxer briefs. You spread the overlapping fabric apart to access the opening.
- Side fly: The opening sits on one side rather than the center front. It uses a double fold of cloth with no closure mechanism, so you simply reach in from the side.
- Button fly: Most common on loose-fitting boxer shorts, this is essentially a vertical fly secured with one or two buttons. More secure, but takes a bit more effort.
- No fly: An increasingly popular option with no opening at all. Users go over the waistband instead.
A Feature With Deep Roots
The fly became a defining feature of men’s underwear as commercial manufacturing grew in the early 20th century. Innovations in front fastenings were a major selling point as companies competed for customers. Cooper’s, the company that introduced the Jockey brief in 1934, patented an inverted Y-shaped seamed fly opening that was considered revolutionary at the time. That Y-front design became so iconic it shaped how people thought about men’s underwear for generations.
The fly wasn’t just functional. Its seam lines drew attention to the front of the garment, giving underwear a more structured, intentionally designed look compared to the plain drawers men had worn previously.
Why Many Newer Designs Skip the Fly
If you’ve shopped for underwear recently, you’ve probably noticed that a lot of boxer briefs and trunks don’t have a fly at all. This isn’t an oversight. It’s a deliberate design choice driven by several shifts in how men dress and what they expect from underwear.
One argument is purely practical. Ricky Choi, co-founder of underwear brand Nice Laundry, has called the fly “somewhat of an antiquated concept,” pointing out that using one is a two-handed operation. Going over the waistband, by contrast, can be done with one hand. With fewer men tucking in their shirts and more elastic-waisted pants in rotation, pulling the waistband down has become the easier option for many people.
Fit plays a role too. A fly requires overlapping layers of fabric in the front panel, which can bunch up or create visible lines under slim-fitting pants. Sean Radford, Jockey’s director of design, has noted that as clothing has gotten slimmer over the past decade, a flyless front simply looks cleaner and sits flatter against the body.
There’s also a support advantage. Flyless designs are constructed with a continuous pouch in front, which holds everything in place more snugly than a fly with overlapping fabric panels. That makes them a better fit for physical activity, which matters as the line between everyday underwear and athletic underwear continues to blur. As one brand executive put it: “There’s a place for everything, and everything in its place.”
Fly or No Fly: What Actually Matters
Whether the fly is useful to you depends mostly on how you dress and your personal bathroom habits. If you wear dress pants with a belt and a tucked-in shirt, a functional fly saves you real time and hassle. If you live in joggers and untucked tees, going over the waistband is faster and you’ll never miss the opening.
Comfort-wise, flyless designs tend to offer a smoother feel with less bunching, while fly designs give you the option of a little extra airflow through the front panel. Neither choice has a meaningful impact on health. It comes down to preference, your wardrobe, and whether you’ve ever actually used the fly or just ignored it your entire life, which, if surveys of men’s habits are any indication, is more common than the underwear industry would like to admit.