When customers kept crashing their cars into the rickety metal fence around his Washington Boulevard car wash, or flattening tires as they pulled up to the automatic ramp that guides the vehicles along, manager Charles Jay figured he had to do something.

So he put up a sign banning cell phone use at the Homewood-based establishment, hoping to encourage drivers to stop chatting and pay attention to where they are driving.

Jay isn't the only manager in town who's tired of trying to serve distracted -- and distracting -- patrons who are tethered to their cell phones while trying to do business with him.

A flurry of signs, some more polite than others, have popped up in restaurants, stores, banks, post offices and other service-oriented businesses requesting that customers turn off their phones.

"It's so rude. I put these two signs up because people are standing in line telling all their business where everyone can hear," said Iona V. Comer, who posted two computer-printed requests at the Hill District's Dwelling House Savings and Loan Association.

It's easy to miss the black-and-white signs amid the other postings on the bank's brown walls.

But if you do, Comer is happy to remind you.

She hung the signs more than two years ago because of the constant ringing and stream of customers yapping away on their cell phones while she and her colleagues were trying to assist them.

"It gets difficult to do business when people are arguing over the phone or making plans for the evening -- loudly," added assistant treasurer Samuel Milliner.

Beyond the places where cell phones are an obvious no-no -- theaters, hospitals and private clubs -- managers and employees of high-traffic businesses say they sometimes wish cell phones would just disappear. Customers who need to remain connected while being serviced, they said, should just be ignored.

"If someone's talking on their cell phone, I just skip to the next person in line," said a sales clerk at the Subway Sandwiches in Market Square, which has a no-cell-phone sign posted on its counter.

Other restaurants, especially those trying to serve food quickly to waiting lines of customers, have similar warnings.

"It's a matter of common courtesy," said Tony Baverso, the owner of the cafeteria-style George Aiken's restaurant, also in Market Square. Despite his restaurant's posted request that cell phones not be used while ordering food, Baverso said, in many cases customers don't notice it -- or pretend not to.

"We still have problems [with cell phones], but we don't want to lose customers," he said.

In other cases, he said, some customers become agitated -- even angry when he and his staff ask them to turn off their phones so they can take their order correctly.

Baverso said he wonders how they would react if he and his servers told them to delay placing their food orders while they took a phone call.

An employee across the street at the Jenny Lee Bakery did just that.

The bakery used to display several signs that read simply "No Cell Phones Allowed," but they were removed in December when the corporate office deemed them too brusque.

Now the signs are crisp and genteel, explaining to customers that they will be better served once they cease using their cell phone.

"We reworded our sign to be more customer-friendly," said manager Dan Konieczny.

One clerk, Kathleen Ciganik often pulled out a toy cell phone and began talking on it if a customer would approach her while immersed in a conversation. "My toy phone actually rang and I would say, 'Hello, may I help you?' " She'd then serve the customer once the cell phone was put away. There are no signs at a Starbucks in Shadyside, but Eric Lowman wishes there were. His customers regularly order their complicated coffee drinks and carry on phone conversations, often without acknowledging him. Signs, he sighed, are not allowed in Starbucks.

"We're not allowed to be rude like that," he said.Since the advent of the steadily shrinking and increasingly ubiquitous mobile devices, etiquette experts have reminded cell phone users that there is a right and wrong time to use them.

But businesses have their own rules of engagement.

"The bottom line is service. How can you serve your customers effectively if you have to make 10 people wait while someone's talking on their cell?" said Diana Svoboda, spokeswoman for the Pittsburgh region of the U.S. Postal Service, where a smattering of branches have decided to put up "no cell phone" signs.

"When a customer on a cell phone says, 'Wait a minute, wait a minute,' it detracts from the customers in line behind them," she added.

But Svoboda added that she, too, has been guilty of bad cell phone behavior.

Svoboda said she felt bad a few days ago as she stood in line at another no-cell-phone establishment -- the Giant Eagle grocery store in Monroeville -- as her cell phone rang.

Her job, she said, requires her to keep her mobile phone on constantly, even at inconvenient moments. In front of the sales clerk, she had to answer it.

"If I'd been farther back in line, I would have stepped outside. I was upset, I could've caused her to make mistakes," she said.

Don't expect the cacophony of noise, people loudly exposing their private lives on cell phones and the ensuing showdown of barbs between business owners and passersby to cease anytime soon. Cell phone sales show no signs of slowing down.

By the beginning of 2004, about 64 percent of households said they had at least one mobile phone, according to San Francisco-based Forrester Research wireless analyst Charles Golvin. The biggest growth in wireless over the past two years, he said, has been in how many cell phones a household owns.

"More than half say they own more than one," Golvin said.

This, coupled with wireless service plans that allow people to be reached at anytime, anyplace and at a low cost, have fueled the legions of users who will talk about anything, anywhere.

"Going forward there's going to be more of a backlash about what is appropriate and what isn't," said Golvin.

Still, since Gray posted the no-cell-phone sign at his car wash, not much has changed.

"Every month, someone new runs into the fence."