Breakthrough ideas often come from the least expected sources.

For Daniel Friedman, the flash came from a woman named Rachel Tutera. Mr. Friedman makes custom men’s suits, mostly for corporate clients in his end of Park Slope, Brooklyn.

Ms. Tutera runs a blog called The Handsome Butch. When she wrote to him last year, seeking a sales job, she had a proposition: Why couldn’t Mr. Friedman, with his expertise in men’s suits, make them for women like her — not women’s suits, but the same gear he was making for guys, with the same masculine profile, but fitted to women’s bodies? It was a question he had never considered.

In a coffee shop near his home the other day, he seemed still struck by the world that opened to him after that initial email.

“The whole thing is really strange, and sometimes I can’t — ” he said, his voice evaporating into the wonder of it all. He was not even sure how to identify Ms. Tutera, gender-wise. Was she transgender or just mannish? Sometimes it was hard to know such things. What he knew was that she had changed his life. “When we started this business, it was for money,” he said. “And now it’s not. It was the emotion, the excitement that people had, that became everything for the company. At least for me. You don’t expect to turn a corner and that’s what you’re going to find.”