The picture is meant to give you a jolt: Against a black background sits a solitary church pew, and above the pew, attached to a set of incongruous headrests, are two bright yellow safety bars, the kind you'd need for a roller coaster at Lagoon. Underneath that is the punch line: "Take the ride of your life."

This is the cover of the slick brochure that landed on doorsteps in Salt Lake City two weekends ago. "Thrill ride theology," begins the text inside publicizing a church known as K2, described as "a modern Christian church of ordinary people seeking an extraordinary adventure with God."

K2, as even the name itself suggests, is hardly the kind of mainstream Christian church that sits stolidly on a street corner waiting for the descendants of former members to grow up and join. But then "stolid" hardly describes most mainstream churches anymore either, in an age of market shares and "branding," the Internet and Christian heavy metal, alternative worship services and ZIP code blitzes.

A generation ago, most churches tended to advertise discreetly on the religion pages of the newspaper, if they advertised at all, and it was easy to argue that these low-key displays, with their listing of that week's sermon topic, were more like notices to the faithful. These days, though, even mainline Protestant denominations hire advertising agencies. Often they have their own tag lines and logos and TV ad campaigns.

There are advertising companies that specialize in religious marketing and demographics. The Church Ad Project, headquartered in Winsted, Minn., has been around for 25 years and has helped 20,000 churches conduct marketing campaigns, according to a Church Ad spokeswoman. The Breakthrough Media Group in Providence Forge, Va., describes itself as "20-year leader in church marketing" with a "direct mail strategy using jumbo full-color postcards."

Don't forget the "all important four-second rule," advises the Church Ad Project on its Web site. "The average direct mail piece has an initial four seconds in which to begin the communication process. There must be something humorous or intriguing that captures the eye."

Church Ad's postcards are both. "You don't need a modem to 'get connected' with God," reads a generic postcard for sale to any number of churches. "Comes with an after-lifetime guarantee," says another. Breaththrough Media Group's postcards, too, are designed to turn a familiar phrase on its ear, as in: "We don't want you to fill a pew, we want you to fulfill your purpose."