NEW YORK - The best time to turn a pay phone into a lending library is early on a Sunday morning, said John H. Locke, an architectural designer who may be the world's leading expert on the subject.

"There aren't a lot of people out," he said. "You can just go down, find a good booth, carry it out, latch it in. It takes seconds. And then just fill it up with books and let's wait and see what happens."

Last winter, Mr. Locke designed a lightweight set of bookshelves to fit inside the common Titan brand of New York City pay phone kiosks. A fabricator in Brooklyn cuts the shelves, which Mr. Locke paints and assembles in his apartment. So far he has carried out four installations, most recently at Amsterdam Avenue and West 87th Street just before 8 a.m. on a Sunday.

Mr. Locke snapped a lime green bookcase into place, stocking it with children's books and paperback novels.

He had barely rounded the corner before a man who had been standing outside the deli began browsing through titles, choosing "The Shining" by Stephen King.

What happens to the installations after the first few minutes is a bit of a mystery to Mr. Locke. He checks on them periodically, he said, until they disappear - after a few days or a few weeks. Which is fine with him.

"It's a spontaneous thing that just erupts at certain locations," he said. "People like it, people are inspired by it, but then it disappears again."

The libraries have their fans. Publishing houses, bookstores and neighbors have approached Mr. Locke to donate books for future installations. The project is currently being featured in the publication Spontaneous Interventions.

If any fixture of city streets cried out for repurposing, it would seem to be the pay phone. The city's Department of Information Technology and Telecommunications began soliciting ideas in June about what to do with the city's remaining 13,000 sidewalk pay phones.

Not that they are completely obsolete. The average pay phone here was used to place six calls a day in 2011. And pay phones brought the city $18 million in revenue in the last fiscal year, mostly from advertisements displayed on the side of the phones' cabinets.

Since the agency would be loath to give up that money, it is considering suggestions that it turn phone booths into touch-screen neighborhood maps; convert them into charging stations for mobile devices or electric cars; or use them as dispensers for hand sanitizer. It is also engaged in a pilot project to use pay phones as Wi-Fi hot spots.

Mr. Locke, who has an aversion to outdoor advertising, said he wanted nothing to do with the city's initiative. He does post the plans for his shelves on his Web site, in the hope that people will install their own versions in their own neighborhoods.

After Mr. Locke had installed the shelves and headed back home to have breakfast with his fiancee, four men arrived who were very interested in the project. They spoke in hushed tones and glanced up and down the block. One pretended to use the phone peeking out of the bookshelf. Then, the coast clear, they emptied the shelves of their contents. Everything went into their blue plastic bags, from "Leverage Leadership: A Practical Guide to Building Exceptional Schools" by Paul Bambrick-Santoyo to "The Short Stories of F. Scott Fitzgerald." The men shouldered the bags and went their separate ways.

Behind them they left an empty bookcase, now good for nothing - unless someone was actually looking to make a phone call.

The New York Times