Holding a half-crocheted aqua kippah in her left hand, Ronnie Selbst picks up one of the many phones on the steel column behind her and says, "Bid a half and three-eighths for a thousand."

Wearing the same light-blue jacket as the other 20 traders in the horseshoe section of a trading floor of the American Stock Exchange in New York City, the Montclair, N.J., woman stands out not only because she is one of two females, but because of her unusual pastime — crocheting kippot for charity between trades.

Selbst, 42, who has owned an exchange seat for 10 years, trades equity options, primarily for Chase Manhattan Corporation and W.R. Grace Co. It takes about five seconds to do a trade, says Selbst; on busy days, she makes about 150 trades, on slow days only about 25.

To keep busy during slow days, Selbst turned to crocheting. "When days are really busy, I have to put it aside. But with [slower] days like these, I can do it."

What started as a personal project has turned into a fund-raising plan for her synagogue. Selbst began making kippot at work just over a year ago, after she joined B'nai Keshet in Montclair.

Wanting to wear a yarmulke like the other female members of the Reconstructionist synagogue, Selbst decided to use her spare time at work to make kippot for herself and her daughter. Then she crocheted kippot for the 19 b'nai mitzvah students in her son Andrew's class.

Some months ago, co-worker Jay Knopf asked Selbst to make him a yarmulke with his name on it. When Selbst finished the purple- and light-blue skullcap, Knopf offered to pay her. Selbst suggested he make a contribution to her synagogue instead.

That was the inspiration for her notice in the synagogue's newsletter: Anyone who donates $100 or more toward the synagogue's Torah fund will receive a crocheted yarmulke from Selbst. So far, she's collected $800.

Now Selbst has gone on to a more ambitious project: raising money to help build B'nai Keshet's first permanent house of worship. The deal is the same: Selbst will custom-crochet a kippah for anyone, member or not, who donates at least $100 to the synagogue.

Raising funds for B'nai Keshet means a lot to Selbst. "After years of not identifying with any religious aspect of Judaism and after finding B'nai Keshet — it's what I've been looking for," Selbst says.

By now, Selbst's crocheting setup is a familiar sight to her co-workers. At her feet on the gray floor among the white ticket scraps sits her Dress Barn bag filled with yarn, along with a red, green, blue and yellow backpack that holds other supplies.

With her white spool of yarn on the counter, crochet hook in hand, Selbst stands and crochets from 9:30 a.m. to 4 p.m., as she stares at a wall full of tiny, bright-green stock quotes on black computer screens.

Crocheting at work is "fairly unique," admits Selbst's co-worker, options trader Michael Longfellow of New York City. Longfellow says he prefers to read books or magazines, but "everyone has their own way of buying the time."

Some people sleep, others eat, says options trader Andrew Vaccarro of Hoboken. He says he "thought it was odd at first," but is now used to Selbst's craft. "Ronnie is rather aggressive in the way she trades and the way she crochets," Vaccarro says.

Knopf, Selbst's first customer and vice president of Spear Leeds and Kellogg, teaches one of his co-workers Hebrew when it's slow. And he organizes a minyan Monday afternoons in a conference room at the exchange.

Penelope A. Collins, who runs the options behind the counter for Spear Leeds and Kellogg, admires Selbst for having the courage to crochet at work, an activity some working women might see as "taboo," Collins says.

With few women on the floor, "we tend to have to go the extra mile to prove ourselves and establish our reputations," says Collins.

"But I think it's good that she's crocheting," Collins adds. "It shows she feels confident about her position."