As Douglas Funk strolls through entrance No. 3 on the lower level of the Springfield Mall it is 7 p.m. and already, weighted down with a duffle bag stuffed with a change of clothes, a toothbrush and an over-sized radio, Funk has been in and out the glass doors five times since he first arrived at around noon.

By the end of the evening he will have flushed down a pepperoni turnover from Pizza Delight with a Pepsi from Taco Laredo. When the last of the mall's 180 shops shuts down at 11 p.m., Funk finally will leave, headed for a party, a bunk at a friend's house, or a room in a nearby motel.

But if he does not get work the next day unloading freight for a local moving company, the 21-year-old Edison High School dropout and convicted burglar will be back at the mall by noon the next day.

"The main reason I come here is so that I can spend time with my friends," says Funk, a personable and well-spoken young man who grew up in a three-bedroom split-level in Fairfax. "I'm unemployed and I really don't have anything else to do or anywhere else to go, because of my lifestyle."

Douglas Funk is known as a "Mall Rat." That is the name given to him and others in the clan of teen-agers and young adults who endlessly stroll the cavernous shopping center in Springfield. These sons and daughters of bureaucrats, teachers, construction workers and military employes are lured to the mall by friends, conversation and the chance to hang out.

"We all got to meet somewhere," says 18-year-old Carl, who estimates that there are at least 75 teen-agers and young adults who frequent the mall often enough to be considered members of the unofficial Mall Rat pack. "You can't fit 75 people in my basement."

So the Mall Rats spend anywhere from all day and evening at the mall to a few hours every afternoon between school and homework. They shift from place to place, moving in small knots, unnoticed by the average shopper. But mall security guards and merchants know them well as members of a small world visible only to those who either belong to it or are close at hand.

"You see the same people day after day, all day long," said Tom Broughton, a salesman in the television and stereo department of the Montgomery Ward store that leads into the mall.

Among the mall regulars are:

Carl, a clean-shaven 18-year-old who does not like the Mall Rat label that security guards and merchants have pinned on the group.

"Do I look like a rat?" asks Carl, the son of a bus driver and cement mason. "Most of us are from middle-class families."

"Baby Opie," a lanky 18-year-old who has spent most of his free time at the mall since he dropped out of first Annandale and then Jefferson High School. He says that he is trying to get a job with Giant Food.

Judy, an employe at the mall on weekends who hangs out there with friends on weeknights. Her buddy is half an hour late, and Judy, 18, drags on a cigarette and grumbles, "I think I been snaked."

Paul, 24, a quiet loner who spends some of his days in a downtown Washington computer keypunch course and most of his evenings at the mall. "I just come," he says softly, his back pressed against a wall, legs sprawled on the floor in front of him. He rolls his head back, shuts his eyes and is quiet again.

Despite their numbers, the youths pose few problems for the mall, officials say. But a number of merchants recalled that more than a year ago throngs of younths congregated at an amusement center and the fast-food shops at the mall's east end, creating trash and noise.

"Sometimes there'd be 50 kids, age 15 to 25, standing around there," recalls mall security chief Matt Shaw, motioning toward a space that once held public telephones. "They had regular numbers people would call them on."

Mall officials say that this contributed to a decision to remove the seats and some of the telephones from the area. Also, Shaw was hired. Since then, the burly ex-infantryman says, he has chased kids who set off the mall's sprinkler system, shot out the tires on his Bronco Jeep, or bunked down for the night in a seating niche. Just this month, Shaw says, he reunited a father with his three runaway sons, aged 8, 10 and 11.

Three stacks of files and snapshots remind the 50-year-old Shaw which youths have been banned from the mall, most of them temporarily, for offenses that range from shoplifing to, as Shaw puts it: "Fightin' drinkin' and cussin' . "

Shaw's main job is to enforce the state's loitering law. "We first spot 'em," he says, "and give 'em about30 minutes." It all makes for a good-natured rivalry, with Shaw as friend and foe at once.

"Not a bad dude," says one Mall Rat.

"They're more of a nuisance than anything else," says Shaw.

Still, there are complaints from some of the merchants along the east end of the mall, where Funk and many other youths often gather.

"I've been to a lot of malls, but these kids are the worst," says Anita Byrne, Manager of Roy Rogers restaurant. "They may stop some people from coming down to this end of the mall."

The so-called Mall Rats are not banned from the privately owned mall entirely, Shaw says, because they rarely break any rules.

"They just hang out in front and are real loud," says Byrne, who echoed other merchants in saying the youths make few purchases. "They're not blocking our entrance so what can you do?"

"I've tried to show furniture with them sitting on it," says Montgomery Ward saleswoman Judy Nash. "Our policy is not for people to abuse the furniture but there's no law that says they can't sit on it."

So, in frayed and faded jeans and long, tousled hair, the youths rest on couches in Montgomery Ward's furniture department and watch television, feed tokens into the machines in the Time-Out amusement arcade, smoke cigarettes while leaning against the foot of a winding staircase, and recline on benches in front of Kitt's Music store.

"You really have to wonder why don't they have something else to do," says Broughton, the salesman.

For Funk, the answer is simple. "I'm an ex-thief looking for a job in times of high-unemployment,"he says.

At 18, he was convicted of burglarizing three shops in the mall and subsequently spent 27 months in prison. Without a steady job since then, he relies on friends and on day work, and spends most of his waking hours walking the mall. It is, he says, a way of life that began when he was 14.

"I didn't become aware that he was spending so much time at the mall until much later," recalls his mother, Marilyn Funk. "I didn't like him spending so much time there . . . but it becomes a part of their life. It's like a second home."

And while others come and go, Funk remains.

"I've been here through about three generations of Mall Rats," he says. This seniority makes Douglas Funk well known to both fellow Mall Rats and to mall merchants.

Says a 15-year-old West Springfield High School School student, "He's everbody's friend."

Says Mike Ganci, who has worked at the mall's Pizza Delight for seven years: "I know Doug. Everybody knows Doug . . . . He burglarized me twice."

Funk says that he has looked unsuccessfully for work in restaurants, garages and even at the mall, although he acknowledges that it is unlikely anyone there would hire him after his burglaries.

"I probably couldn't get a job here now," he sighs at the end of another evening. "Unless I go down to the other end, where they don't know me."