It's one thing to hire cashiers, clerks and ice cream scoopers, train them and trust them for a summer's worth of work. But try hiring 42 summer cops, training them, handing them guns and putting them on the street.

Island police chiefs have to do it every year, and it's a task fraught with risk and worry.

"These people are carrying a badge and a gun under the color of your town," said Chilmark police chief Tim Rich, who this year hired five summer police. "You train them as best you can, and you go with your best instincts."

Police have little choice in the matter. With population on the Island exploding in the summer, the year-round ranks can't handle the increased volume of calls all by themselves. They need reinforcements, and in some towns, summer cops actually outnumber the full-time force.

As Chief Rich put it, it's also a matter of economic reality. No Island town could afford to fund a year-round force at the level needed in the summer. So summer policing is a fact of Island life, but that doesn't necessarily make police chiefs sleep any better.

A few years back, Edgartown police chief Paul Condlin actually opted for more overtime from his seasoned year-round officers rather than rely on summer police, who were just too green for the work.

"Policing today is different from what it was when I started in 1977," said Chief Condlin. "The summer officers could handle calls such as domestic disputes or drunk drivers without much training, but today that's not the case. Not only do we have liability concerns, but we're mandated to respond in certain ways to situations."

The other worry is community relations. Summer police are not tucked behind desks back at headquarters. They are out on the sidewalks, right in the thick of it all.

"They're even more visible in the public eye than full-time officers are," said Chief Condlin, who this summer oversees 10 summer police. "They're on the street downtown in contact with the general public a good percentage of time, while full-time officers are out in the cruisers handling calls."

The risk is clear. One bad experience with a summer cop can color a citizen's view of a town's entire police department. "How they present themselves can really, seriously damage any progress we've made," said Mr. Condlin. "You have to monitor them closely."

And at some point, he pointed out, more staff is not better. "It's difficult to manage the special officer staff," he said. "It's not helping to add more people who don't have the experience. It can just add more confusion."

So, what's the solution? For Chief Condlin, it has meant cutting back some of the summer police and shifting money into overtime budgets. But for all the Island police departments, including Edgartown, the answer has been more training. At a minimum, all summer officers now complete a one-week course on the Island run by the Criminal Justice Training Council, a state agency.

Town police augment that week with more training, but even if the total hours reach 120, that's still just a fraction of what year-round officers received in 24 weeks at the police academy. "The month of June is pretty much training," said Chief Rich. "So the people are good to go by Fourth of July weekend."

Chief Condlin concedes the learning curve is steep, especially for the greenest recruits. "It's a lot of information," he said, "and a lot to comprehend for someone for whom this is the first experience in policing."

Last year, Oak Bluffs police actually surveyed their summer police officers to find out what they needed and what was lacking in the way of training. "Summer police strongly felt that when violent encounters took place, they weren't adequately trained to handle it," said Oak Bluffs police Lieut. David Roberts.

This year's additional training, he said, put a heavy emphasis on the use of force. Summer officers doubled the amount of time on the firing range with pistol instruction. Plus, recruits tested their wits against an interactive computer program called Range 2000.

The program simulated real events that a police officer might face. "Range 2000 was the most useful training tool. We actually practiced what could happen," said summer officer Bill Mackenty, 31. In his third summer now as a police officer in Oak Bluffs, Mr. Mackenty, who is a teacher in Edgartown, said this year' training made him feel much more confident.

In one scenario, he explained, officers practiced responding to a report of a suspected breaking and entering. "If you didn't identify yourself (as an officer), then the owner comes out with a gun, and he gets dusted," said Mr. Mackenty. "If you did identify yourself, the owner comes out and tells you he was just working late."

Mr. Mackenty and Oak Bluffs' other 14 summer officers also received extra training in defensive tactics and how to arrest someone. "Let's say you have a guy who's drunk and disorderly. When you have this level of training," he said, "we're able to arrest him in a way that looks a lot more professional and in a way that nobody gets hurt."

But even before training can begin, there's the hiring process. Over the years, that task has been plagued by the same woe every other Island employer faces - housing. The job pays, on average, $12 an hour. In Aquinnah, police chief Doug Fortes still doesn't know if one of his summer recruits can stay because he can't find an affordable place to live.

West Tisbury police chief Beth Toomey said her department manages to come up with creative solutions to the housing problem. Her summer force has grown from one to a total of five in just two years. Chief Toomey has tried home-growing her own summer force, mining talent that already lives here.

Case in point is Deanna Cote, a 21-year-old West Tisbury resident who was graduated from the Island high school in 1997. For the past two summers, she worked the Seth's Pond beat, unarmed, dealing with traffic and parking issues. But with Chief Toomey's encouragement, Officer Cote completed some training at the police academy and finished her firearms qualification.

Now an armed officer, she's moved up from Seth's Pond to the airport. "This is an Island kid we developed," said Chief Toomey. "I really want to develop Island people into these positions."

For the summer recruits, one incentive is giving them the hands-on experience they want. Applicants for these jobs, said Chief Fortes, are eager to do police work. In Oak Bluffs, summer officer Todd Castro said what attracted him to the Vineyard was that police departments are training summer cops to do real work. "I didn't want to spend my summer writing parking tickets," said Mr. Castro, a 24-year-old graduate of Bridgewater State College.

In some cases, Island police have attracted experienced officers from the mainland to take summer jobs here. Officer Matt Stein in Oak Bluffs is 44, and he's got 20 years experience as a part-time sergeant in the Brookline police department.

Still, most summer police fit the mold of young and eager. But is there such a thing as too eager when youth and police work combine? Lieutenant Roberts says yes, and he takes care to avoid hiring officers who are just in it for the power trip.

"Our application is 17 pages and includes essays, and we do background checks," said the lieutenant. "But it's in the interview where people like that stick out like a red flag. I had one guy sit down and the first question he asks is, 'What kind of guns do you carry?' "

Island police, across the board, champion community policing far more than the Rambo approach. They want the summer police to interact with the merchants, the tourists and the residents. "Right from the get-go, we want that," said Lieutenant Roberts. "We expect more from them than just standing around and looking tough."

Officer Mackenty takes the community policing seriously. "I like balancing the needs of the summer people and the needs of the year-round population," he said. "I try to be understanding. If a year-rounder is parked in a loading zone so he can pick up the kids, you don't have to jump on somebody for that."

Still, no matter what Mr. Mackenty does, he knows the experience of being saddled with the derogatory "rent-a-cop" comment. "It's frustrating to be called that," he said, "especially with all the training we get."

What a lot of people don't know about the so-called rent-a-cops is how many have used the job as an important stepping stone in their careers. Chief Rich said he's kept track of where some 70 summer police he's hired have gone - from the New York City police department to district attorney's offices. Even more important, Mr. Rich said, is that the summer beat is the place where the chiefs of police in Aquinnah, Edgartown, Tisbury and Chilmark all got their start.