If you’re a normal person, you probably don’t spend much time contemplating household hardware: how a hinge holds a door in place, how a knob feels in the hand. Rhett Butler — possessor of the world’s largest collection of fine architectural fittings — isn’t a normal person.

“Hardware incorporates everything,” the bespectacled 50-year-old says on a tour of his cavernous brick factory building, which is located along a sleepy, postindustrial stretch of Brooklyn waterfront. “It’s art, architecture, history, design, technology, manufacturing. It’s in every building on the planet. There’s no end to it.”

That, he says, is what his 23-year-old firm, E.R. Butler & Co., is about: endless possibilities.

For Bill Gates’s 66,000-square-foot (6,100-square-meter) mansion on Lake Washington (nickname: Xanadu 2.0), Butler reverse-engineered door handles from the grip of an antique French dagger. Butler custom designed every last hinge, knob, latch, pull and finial in the nearby Italianate villa of McCaw Cellular Communications Inc.’s Keith McCaw.

Shoji Handles

And when Oracle Corp. (ORCL) Chief Executive Officer Larry Ellison (net worth: $42.5 billion) spent nine years and a reported $200 million to replicate a 16th-century feudal Japanese estate in Woodside, California, he overlooked one thing: locks. So Butler invented shoji handles with invisible latching mechanisms. He’s also supplied hardware to former presidents, leading fashion designers, Nobel Prize-winning novelists and Oscar-winning actors and directors.

The son of a hardware store owner, Butler for years tried to avoid his father’s business. But when the elder Butler retired in 1990, his clients began to pester Rhett, then a graduate student in architecture at Rice University in Houston. (Rhett derives not from Margaret Mitchell’s Confederate creation but is rather a family name.) Before long, Rhett had launched E.R. Butler from a two-bedroom apartment on New York’s Lower East Side.

As the company began to acquire the assets of many of America’s most venerable firms — Enoch Robinson, W.C. Vaughan – - Butler relocated into successively larger spaces before finally settling in a decade ago at the company’s current showroom and headquarters, a landmarked building in Manhattan’s Nolita neighborhood that in the 19th century served as Tiffany & Co. (TIF)’s silver-manufacturing headquarters.

Rigorous Standards

The four-story Red Hook factory building, meanwhile, was formerly a foundry and World War II munitions plant. Now, it’s where many of Butler’s products are produced: 130,000 square feet of machinery, storage and workrooms that extend out in every direction, reflecting Butler’s rigorous standards and sizable ambition. One contraption can slice through solid steel with a pressurized jet of water the width of a human hair. It’s not until we start to climb the stairs to the second floor that Butler’s pulse seems to quicken.

“Wait till you see this,” he says. “It’s basically every catalog from every company in the world that’s ever produced hardware” — 40,000 volumes, an archive decades in the making. “It’s really the history of the industry,” he tells me.

Cloisonne Collection

Moving on, Butler sorts through his growing collection of Japanese paraphernalia — a graceful ivory shoehorn, possibly “the largest collection of cloisonne in the world, including Japan,” before revealing that his company also custom creates “electronic components for some of the hardware we produce: circuit boards and the like.”

“Circuit boards for what?” I ask.

“There are people out there who want secret rooms, lined in concrete or steel, where the entrance is controlled digitally so an intruder can’t figure it out,” Butler says. “I design all the stuff that gets them into and out of that room safely and securely. There are a lot of people worried about kidnapping.”

Having reached the end of the tour, Butler is now speeding across the Brooklyn Bridge in his BMW 750Li, en route to the Nolita showroom. He’s discussing materials — specifically, the strangest, most luxurious materials he’s transformed into hardware.

“We’ve done door handles in coral, resins, pretty much every semiprecious stone that’s out there,” Butler says. “Pearls. Mother-of-pearl. Every kind of wood and metal you can possibly imagine.”

Hidden Bullion

He’s even done solid-gold hardware for a client who wanted his bullion hidden in plain sight. “He gave us the gold; we melted it down into door handles,” Butler explains. “Who’s going to steal the hardware out of a house?”

By the time we arrive at 55 Prince St., I’m beginning to think I would, so long as it were made by E.R. Butler. Inside, glass display cases house a sampling of Butler’s wares. One handle features a lapis lazuli grip; another is made of mammoth tusk excavated in Siberia. Glass knobs are available in 12 shapes, three sizes and a dozen colors. There are four types of bases, six styles of plates and a hundred metal finishes. Do the math, and that’s “something like half a million options — before you even get into custom,” Butler says.

Which brings the high-end-hardware impresario to the subject of musician Lenny Kravitz’s capacious New York apartment. There, visitors are as likely to pet the doorknobs as they are to turn them.

“We came up with the idea of doing ermine,” Butler says. “It just so happened that the length of an ermine pelt is the same length as a lever handle, so we just stretched the body over the grip. We can do pretty much anything.”