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Man of Many: Best Horizontal Fly

Almost nobody uses the fly on their undies. So we turned it sideways.

It's quicker, works with either hand, and it's the first fly you'll actually use. Here's why Man of Many named it Best Horizontal Fly.

What the half-time urinal queue taught me about men's undies

Belt, button, zip, then the fumble. There's a quicker way, and it started out looking like a pocket.

Why Man of Many named this Aussie brand's fly the best

It opens across the top instead of down the front. I'm the bloke who put it there, and this is why.

1,522 customer reviews
Close-up of the horizontal fly on black Debriefs boxer briefs, with an arrow labelled the horizontal fly
Screenshot of Man of Many's 7 Best Men's Underwear Brands, listing Debriefs Boxer Briefs as Best Horizontal Fly

It's half time at the footy. You've had three beers and forty minutes of questioning the ref's eyesight. And now the queue for the urinal runs out the door and halfway down the concourse.

You shuffle forward for most of the break, doing the maths on whether you'll be back in your seat before the siren. Then a spot finally opens up and the real work starts. Belt, button, zip. Then you either dig around for the fly on your undies or pull the whole waistband down.

Most of us pull it down. Over the fence rather than through the gate.

I did it that way for years. I can't remember a single time I used the fly on a pair of undies, and I don't know many blokes who do.

So when I sat down with my manufacturer in Turkey to design Debriefs, I got stuck on a question that sounds a bit ridiculous said out loud. Which side should the fly go on? Put it on the left and it suits one hand. Put it on the right and it suits the other. And either way, most blokes would ignore it and go over the top.

So we tried something different. We turned it around so it opened across the top.

The first samples came back looking like someone had sewn a little pocket on the front. It became a running joke, and for a week or two I was in on it.

Then I started wearing them.

How a horizontal fly works

The opening runs across the top of the pouch, just under the waistband. At the urinal, you unzip your trousers and reach down through the top. Your belt, button and waistband all stay exactly where they are. It works the same whichever hand you use, which is more than you can say for the fly you've got on right now.

Vertical fly
Line drawing of undies with a vertical fly down one side of the pouch

Dig sideways through a slit

Debriefs horizontal fly
Line drawing of Debriefs undies with the opening across the top of the pouch 1 2 3

Reach straight down through the top

1The opening runs across the top of the pouch
2Reach straight down through the top
3Belt, button and waistband stay where they are
Vertical fly
No fly
Debriefs horizontal fly
How you get in
Dig sideways through a slit
Pull the waistband down
Reach straight down through the top
Your waistband
Stays up
Pulled down under everything
Stays up
Which hand
Designed for righties
Either
Either
Gaping
Can gape open
Nothing to gape
Double layer stays closed

"The real genius in these men's undies is the horizontal fly."

"Instead of wrestling with a tight vertical slit when nature calls, the top-loading fly gives you easy access without loosening the waistband."

Man of Many, 7 Best Men's Underwear Brands, 2026. Debriefs: Best Horizontal Fly.

7 reasons the horizontal fly beats the one you never use

1

You'll actually use it

Plenty of undies have a fly. Hardly anyone uses it, because it's a slit down the front you have to dig around to find. So you pull the waistband down instead. I'd bet you did it this morning.

The fly on Debriefs sits right where your hand already goes. Unzip, reach straight down through the top, and you're sorted. No hunting for the gap, no dragging the waistband under everything, no hitching it back up after. It's quicker than going over the top, so it's the one you'll actually use.

★★★★★Customer review

"They are so comfy and the horizontal slot makes taking a pee easy as!"

John K. · Trunks
2

Lefties and righties get the same fly

Model in grey Debriefs boxer briefs, with two gold arrows coming down from either side into the opening across the top of the pouch

A vertical fly has to pick a side, so somebody's always reaching across the wrong way. An opening across the top doesn't care which hand you use. Lefties, righties, the bloke who switches depending on which hand is holding the beer. Same fly.

★★★★★Customer review

"I am confident lefties will appreciate the horizontal fly."

Michael J. · Trunks
3

Yes, it looks like a pocket

Black and white photo of one of the first Debriefs samples, with an old logo and an opening that looks like a pocket
One of the first samples
You can see where the pocket jokes came from.

I'll admit it looks a bit odd the first time you see it. When I handed the early samples round to mates and family, the pocket jokes came thick and fast. Then they wore them for a week, and funnily enough nobody brought up the pocket again.

★★★★★Customer review

"I was a little skeptical about the horizontal fly but it makes complete sense once you put them on!"

Edward B. · Trunks
★★★★★Customer review

"I've actually become a big fan of the fly design. I couldn't imagine using undies with a 'side-opening door' anymore."

Thomas S. · Trunks
4

The fly made the pouch better

The outer layer of a grey Debriefs pouch pulled back to show the second layer of fabric underneath

Moving the opening to the top meant we could double the fabric across the whole pouch. Two layers stretch less, so everything stays where it should. The pouch holds its shape wash after wash, and nobody gets a view they didn't ask for.

And because the pouch isn't pinned to the waistband, it has a bit of give. It settles to fit you, whatever you're working with. I'd love to tell you I planned that part. I didn't. It came free with turning the fly around, and it's still one of my favourite things about them.

5

No seam down the middle

Purple trunks from another brand with a line of stitching straight down the middle of the pouch Centre seam
Grey Debriefs trunks with a small fold at the base of the pouch and no seam up the front Debriefs dart
Stitching straight down the middleOne small fold at the base, no seam up the front

The easy way to give a pouch its shape is to sew two pieces of fabric together straight down the centre. Plenty of brands do it. It works, but it leaves a ridge of stitching along the most sensitive real estate you own. And it rubs from breakfast to bedtime.

If you're one of the many blokes who lost the hood as a baby, you'll know the feeling. A seam there is about as welcome as sand in your swimmers.

So we used what's called a dart, which is a fancy sewing word for a fold. The fabric at the bottom of the pouch folds over itself, and that fold curves it into a dome. That gives the pouch its shape without a seam anywhere near the front. It sits flat and soft, and there's nothing there to rub. It's harder to make that way, and I wasn't budging on it.

6

The fabric's as good as the fly

Close-up of soft grey Debriefs fabric. Made from Lenzing MicroModal: 3x softer than cotton, plant-based from beech trees, breathes and wicks sweat, stays soft wash after wash

None of this would matter if the fabric was rubbish, so we didn't cut corners there either. Debriefs are made from LENZING MicroModal, a plant-based fibre made from beech trees, and it's 3x softer than cotton. It breathes, it pulls sweat away from your skin instead of holding onto it, and it stays soft wash after wash.

Cotton soaks up sweat like a sponge and dries rough, which is why your old undies feel like cardboard by February. Bamboo starts out soft but stretches and loses its shape. MicroModal does neither.

I first wore it while I was living in America in 2016. When I came home, I couldn't find it anywhere in Australia, so I brought it over myself. Then it took 18 months and more than 20 rounds of samples to get the pair right.

7

1,300+ blokes loved them enough to leave five stars

I could tell you all this until I'm blue in the face, but I'm hardly unbiased. Debriefs has 1,522 published customer reviews. Plenty of them bring up the fly without being asked.

Man of Many, DMARGE, GQ and Penthouse have all written about us too.

As featured in

In their words

1,522 customer reviews
★★★★★

"The top flop is fantastic. The vertical fly now seems stupid."

Julian · Boxer Briefs
★★★★★

"The quality is evident from the get go and the access flap at the top makes so much sense that I'm shocked other brands haven't done it before."

Rohit R. · Boxer Briefs
★★★★★

"The horizontal 'fly' section, after some hesitation, is surprisingly way better to use than the usual vertical type."

Tom · Trunks
★★★★★

"Horizontal opening = Aussie ingenuity in action!"

Paul · Trunks
★★★★★

"He's an enormous fan of the unusual fly, since button and Y fronts tend to gape on him."

Mal H. · Boxer Briefs
★★★★★

"Best fly option for men's underwear is the horizontal fly, less fiddly for exits and provides better support."

Shane F. · Boxer Briefs
★★★★★

"That horizontal fly is a game changer for something no guy would even consider thinking about when buying boxers."

Craig W. · Boxer Briefs
★★★★★

"They are very comfortable, don't ride up and the horizontal fly is genius."

Winston D. · Trunks
★★★★★

"The high horizontal opening is much better than the typical vertical slit/overlap used by most brands, as there's less chance of slipping out."

Ben I. · Trunks
★★★★★

"I've been wearing these undies for a few years now… the horizontal fly is an absolute winner! I just bought another 5 pairs."

Rod H. · Trunks
★★★★★

"The horizontal fly is awesome and I don't understand why other underwear companies don't do this."

Brian P. · Trunks
★★★★★

"Very happy with the quality of the fabric, very soft, yet keeps everything in place nicely, and the horizontal fly is a must have."

David G. · Boxer Briefs

Trunks or boxer briefs?

Both have the horizontal fly, the double-layer pouch and the same MicroModal. The difference is the leg.

Model wearing black Debriefs trunks, front view

Trunks

5 cm leg. A shorter, classic cut.

Try the trunks
Model wearing black Debriefs boxer briefs, front view

Boxer Briefs

9 cm leg. More coverage, and the better pick if you're active or have bigger thighs.

Try the boxer briefs

Buy more, pay less per pair

Prices in NZD
1 pair of Debriefs, flat lay
1 pairNZ$46/pairFull price Shipping calculated at checkout
3 pairs of Debriefs, flat lay
3 pairsNZ$42/pairNZ$46NZ$126 totalSave NZ$12 Free shipping
6 pairs of Debriefs, flat lay
6 pairsNZ$38/pairNZ$46NZ$229 totalSave NZ$47 Free shipping
Best value9 or more pairs of Debriefs, flat lay
9+ pairsNZ$36/pairNZ$46NZ$324 totalSave NZ$90+ Free shipping

Mix trunks and boxer briefs in any colour or size. Pack prices apply automatically in your cart.

Free shipping on 3+ pairs

2 guarantees on your order

Love 'em or they're free

You don't have to take my word for any of this. Try them, and if they don't live up to it, it's on me.

1stpair on us

First pair guarantee

I'm a bloke off the internet asking you to buy his undies. I know how that sounds. So I'll take the risk off you.

  1. Try your first pair
  2. Don't love them? Keep them
  3. We refund you in full
First order onlyOne worn pairWithin 30 days of delivery
52wash guarantee

52 washes or 12 months

It took months of searching and a few failed attempts to find the factory in Turkey that makes Debriefs. I stuck with them because they build undies properly, with stitching and elastic that last. If a pair fails within 52 washes or 12 months, we'll replace it.

  • A hole in the fabric
  • Coming apart at the seams
  • A waistband that loses its stretch

P.S.

Next time you're in that half-time queue, it's unzip, reach down through the top, and back to your seat before the siren. Belt still done up. And if they're not for you, the first pair's on us.

Will Thomas

Will Thomas
Founder, Debriefs

Heads up, though. We make Debriefs in batches rather than churning them out on repeat. So when a size sells out, it can take two to three months before the next run lands.