One overcast Sunday morning, Benjamin Talley Smith, an apple-cheeked 45-year-old with a thing for a Canadian tuxedo, was at the Rose Bowl flea market in Los Angeles shopping for jeans.

He was wearing jeans — a beat-up pair of Levi’s and an equally worn Levi’s jeans jacket — and rooting through piles of jeans. He wasn’t looking for collectible jeans, the classics that can fetch thousands, but rather interesting jeans: jeans with an unusual fade or some weird D.I.Y. patchwork or a striking paint splatter.

“Every jean is different,” he said with the air of an oenophile assessing a new bouquet. He was holding up a pair of jeans with some big white patches on the thighs. “Too acid-washed for me,” he said, putting them back.

He picked up another pair, pointing at a series of faded lines at each ankle. “See that honeycomb wear pattern?” he said. “That was because some cowboy had his jeans tucked into his boots. I might try to replicate that.”

Then he spied a pair of old jeans from the Japanese brand Evisu. “Look at that,” he said. He smiled. “I made those.”

Discovering his own work is not an uncommon occurrence for Mr. Smith. If fashion has a man behind the denim curtain — a wizard of jeans — he is it, a name that’s passed from brand to brand, designer to designer, like a secret password.