ason Schultzman works at a nonprofit in Dupont Circle. He plays in an after-work basketball league. And he carries a man-bag. He calls it simply "a messenger." "I won't even use the word 'bag,' " he laughed.

For generations, men have typically left bags to the ladies. But that was before BlackBerries, laptops and digital cameras. In these tech-friendly times, guys just have more stuff.

So why not a man-bag?

After all, modern men are adapting. They've embraced fashion's more tailored silhouette. They're wearing product in their hair. Some are even getting facials.

Which may explain the ubiquity of the urban male's bag. Not easily mistaken for a woman's purse, man-bags are often shoulder-slung messengers (modeled after the carry-alls schlepped by couriers), square flight bags and attaché-like totes. (While many a Hill staffer slings a suede-bottomed JanSport over his freshly pressed suit, it should be noted that a backpack is not a man-bag. It is a child's bag.)

Menswear designers like John Varvatos, Bottega Veneta and Kenneth Cole have been showing more bags each season -- so many that handbag designer Melanie Dizon is getting into the game. Her first design for men, a calf leather, briefcase-style conveyance with smart features like an umbrella/newspaper slot, will be carried at Circle Boutique this fall.

But oddly enough, it seems that a bag's functionality isn't as important as its terminology. Simply put: One man's murse is another man's messenger.

Schultzman scoured the area looking for the right bag -- durable and comfortable, yet stylish. He finally settled on a navy Jack Spade. "My friends bust my chops for having a 'murse,' but it's simple and it holds everything. Even my lunch and gym clothes."

Marshall Thompson, owner of British-purveying shop The District Line, has proudly carried his Fred Perry bag for years. "It's professional, but has some edge to it too," he said. "They're actually our best-selling bags here."

Like anything worn on the body, the bag one carries conveys a specific image. Fred Perry's retro design emotes cool, hipster confidence, while giveaways from conventions, embroidered with company logos, broadcast the wearer's sheer laziness or, at best, frugality.

Christopher Reiter, proprietor of Muleh, doesn't sell men's bags, of any size, at his shop. "I guess those bags denote a certain urban style, but I don't think it projects a very strong image for a man."

Reiter lugs his loot around in a sleek aluminum briefcase, but sports it with ripped jeans for a splash of irony. "You can't walk into a grown-up meeting with a man-bag," he said. "But on the flip side, you can't ride a bike with a classic briefcase."

If one thing's clear about the man-bag debate, it's that there are explicit rules of etiquette. For instance: It doesn't need to match your shoes, but it should match your environment (read: no patches, pins or embellishments in buttoned-up offices). To avoid it looking too purse-y, sling your satchel diagonally across your chest. And don't get one that looks like a wallet with a strap -- that really is a murse.

Follow these rules and you can proudly defend your manhood. Unless advocacy isn't really your bag.