The zipper is one of those inventions – along with the bicycle – that seems as though it should have occurred much earlier in history.

How complicated could it be to assemble two wheels, two pedals and a chain? Or to align two jagged strips of metal teeth and shuffle them together? There is no complicated chemistry here, no harnessing of invisible wavelengths. And yet the modern bicycle didn’t appear until the late 1800s, and the zipper didn’t really become the zipper until 1917 (when it was patented by a Swedish immigrant in Hoboken, N.J.).

More confounding still: Now that the zipper has been around for nearly a century, you’d think that something so simple might have been perfected – becoming a 100 percent reliable commodity. There are still tons of faulty zippers out there. Teeth that break. Pulls that pop. Herky-jerky sliding and irreparable lockups.

One zipper gone wrong can render an entire garment unwearable. Thus consistent quality is a must for reputable fashion brands. For decades now, apparel makers who can’t afford to gamble on cut-rate fasteners have overwhelmingly turned to a single manufacturer. YKK, the Japanese zipper behemoth, makes roughly half of all the zippers on earth. More than 7 billion zippers each year. Those three capital letters are ubiquitous. How did YKK come to dominate this quirky corner of industry?

Founded by Tadao Yoshida in Tokyo in 1934, YKK stands for Yoshida Kogyo Kabushikikaisha (which roughly translates as Yoshida Company Limited).

The young Yoshida was a tinkerer who designed his own customized zipper machines when he wasn’t satisfied with existing production methods.

One by one, Yoshida brought basically every stage of the zipper making process in house: A 1998 Los Angeles Times story reported that YKK “smelts its own brass, concocts its own polyester, spins and twists its own thread, weaves and color-dyes cloth for its zipper tapes, forges and molds its scooped zipper teeth . . .” and on and on.

YKK even makes the boxes it ships its zippers in.

And of course it still manufactures its own zipper-manufacturing machines .

With every tiny detail handled under YKK’s roof, outside variables get eliminated and the company can assure consistent quality and speed of production.

Yoshida also preached a management principle he termed “The Cycle of Goodness.”

It holds that “no one prospers unless he renders benefit to others.” In practice, this boiled down to Yoshida striving to produce ever-higher quality with ever-lower costs.

It seems intuitive, but it’s far from easy to do. And in the end, the secret to YKK’s success is equally uncomplicated but equally impressive: YKK makes incredibly dependable zippers, ships them on time without fail, offers a wide range of colors, materials, and styles and never gets badly undercut on price.

“There have been quality problems in the past when we’ve used cheaper zippers,” says Trina Turk, who designs her own line of women’s contemporary sportswear.

“Now we just stick with YKK. When the customer is buying $200 pants, they better have a good zipper. Because the customer will blame the maker of the whole garment even if the zipper was the part that failed.”

A typical 14-inch “invisible” YKK nylon zipper (the kind that disappears behind fabric when you zip up the back of a dress) costs about 32 cents. For an apparel maker designing a garment that will cost $40-$65 to manufacture, and will retail for three times that much or more, it’s simply not worth it to skimp.

“The last thing we want to do is go with a competitor to save eight or nine cents per zipper and then have those zippers pop,” says Steve Clima, Turk’s senior production manager.