BELIEVE IT OR NOT, there was a time when T-shirts and flip-flops were considered beach-only attire, when being properly dressed meant wearing a hat -- a pillbox or fedora, a broad-brimmed straw or a cloche festooned with feathers. No matter the style, a hat was the finishing touch on any outfit. And a proper lady -- particularly of the African American Baptist persuasion -- never went to church without carefully donning one.

"I think anyone can be a hat person," says Emilio Sosa, costume designer for "Crowns," the wildly popular musical returning to Arena Stage for a third straight summer. "I love hats. My dad wore hats through all my childhood. . . . Then for a long time hats weren't in fashion. I grew up in the '80s and we had [some] hats in the '80s -- berets, little black hats. In the '90s, hats fell off the meter."

Arena's basement costume shop has a kind of magical aura that Geppetto would appreciate: dressmakers' stands, cutters' tables, sewing machines, and boxes of rhinestones, ribbons, buttons and faux jewels fight for attention amid endless yards of fabric. This riot of color and texture is crucial to the success of "Crowns," Regina Taylor's gospel-inspired show that lovingly details the lives of black church-going women through their own singular relationships with hats.

Sosa's designs have brought him recognition on Broadway and regional stages as well as on television, but until he began working with playwright-director Taylor on "Crowns," hats had not been a part of his design repertory.

"Theatrical hats are different from street hats," Sosa explains, surrounded by 30 or so of his creations. Some are festooned with faux egret feathers, others bedecked with everything from Swarovski crystals to rhinestones, pipe cleaners to velvet and satin. "I had to learn functionality and sturdiness. They had to last. These hats go on stage at least eight times a week. They get sweated on. They get tossed."

Still, though his labor-intensive toppers are crucial to the success of "Crowns," Sosa is quick to point out that this is "not a show about hats. It's about people, and the hats help tell the story . . . about families, about traditions, love, life. The hats just give it that extra little nod."

Taylor got an extra little nod from Michael Cunningham and Craig Marberry's 2000 book "Crowns: Portraits of Black Women in Church Hats," on which she based her script. Many of the 53 women featured in photographs and interviews became composites for her characters. Velma (Gretha Boston), for instance, is a self-described hat queen.

"She likes everything on her hat," Sosa says. "Bells, whistles, glitter. Her hats are always theatrical. They're big, floppy -- they move, and they have glitter, feathers, anything that shines." Mother Shaw (Barbara D. Mills), meanwhile, is the church matriarch whose hats are "big and churchy." Jeanette (LaVon D. Fisher) is "young, sassy, single, flirtatious," and so are her hats.

"I go to Abyssinian Baptist Church on 130th Street in Harlem," Sosa says, "and I see all these hats women wear and it's such a cultural thing: hats and women. On Sundays I see ladies in hats all over the neighborhood, from old ladies to little girls with their mothers. I see generations of hats."

"What's beautiful is that there's a hat for every emotion," adds Joseph Salasovich, Arena's costume shop manager and Sosa's assistant in building "Crowns's" bejeweled and befeathered creations. "There's a hat for a funeral, there's a hat for a wedding, there's a hat for church, a hat for flirting."

And attending a performance of "Crowns" has become a kind of churchlike experience in itself. "People who come to the show start wearing hats," Salasovich says. "These ladies are coming in with these amazing hats themselves," so many of them that the theater makes a preshow announcement reminding audience members to remove their hats so others behind them will be able to see.

And for the bare-headed? Not to worry, Arena has persuaded local milliners to sell their wares at the theater before and after the intermission-less show. With that in mind, here are some tips for novice hat wearers, in the words of one "Crowns" character:

"You shouldn't wear a hat wider than your shoulders. Elongated or oval faces look better with wide brims. Rounder faces look better in the derby style. Hats should be simply decorated. Some women think the more stuff you can fit on your head the better, and I've seen hats that look like lampshades. . . . Some people can't afford to put a whole lot of money into a hat. But the truth of it is, if you buy a cheap hat, you might see yourself one day."

Mother Shaw (Barbara D. Mills, left), Mabel (Angela Karol Grovey), Jeanette (LaVon D. Fisher), Yolonda (Roz Beauty Davis), Wanda (Joy Lynn Matthews, back), Velma (Gretha Boston). Rob Barnes as the Man and Roz Beauty Davis as Yolonda in Arena Stage's hit "Crowns." A hat is more than just a hat to characters such as Yolonda (Roz Beauty Davis) in "Crowns."