From the 31st floor of Twin Towers, a jungle of naked steel scraping sky above Washington, Ernest Jennings can almost shake hands with the pilots of planes sliding in over the Potomac.

Beneath him, Arlington is like an ant farm of cars and people milling in miniature. Across the compass points, the capital spreads out in a dizzying display of green hills and matchbox-sized monuments.

"Being up here is like being in another dimension," says the 28-year-old Jennings."It just fascinates you, 'cause you're in your own little world. Everything down there is like a little Monopoly set."

Jennings, who rolls his words in the syrupy drawl of Louisa, Va., puts his life on the line daily for the pleasure of that view. With shaggy, long blond hair matted with sweat, undershirt and blue jeans wearing thin and smeared with grime, he's one of 45 ironworkers pushing the first of Rosslyn's Twin Towers office buildings, the area's tallest, toward their 340-foot completion.

In this aerie, where men walk four-inch beams without safety lines and make steel sing a tune to the torque wrench, a missed step is known simply as "falling through the hole."

Fear has no place on the reddish I-beams. "By the time you get scared," said James Hale, a burly foreman, "it's usually too late."

The federal government didn't want the $40 million towers rising above Washington's skyline. But the feds lost their court battle to keep the towers small -- to the immense delight of the ironworkers.

Looking down on the world from a perch 31 stories high, Jennings and the rest consider themselves a cut above mere earth-bound species.

"People don't bother you up here," says David Goodwin, a 25-year-old, also from Louisa, a rural county 80 miles from Washington where the tallest building is the 50-foot-high courthouse. In Rosslyn, Goodwin is known as "punk" because he is just learning the girder jockey trade.

"There's nobody to say you can't just pack it up at 8 a.m. if you want. Nobody can stop you from leaving any time you please for another job in another town."

Goodwin, Korean-born, with a long shock of thick, black hair and a wrestler's physique, may be a "punk," but he's learning fast.

He's learning the dance of the ironworker, a slow waltz across beams suspended above 300 feet of yawning emptiness, a terrifying tango on a steel rail that sways like a reed under a man's weight.

On that beam, the wind whispers death in your ear.

Several ironworkers die each year in falls around the country. On Oct. 12 when the building was but two stories high, George Lucas, 50, of Clinton, fell to his death.

Last week, near the building's top, 28-year-old Benny Baker from Damascus rolled off a wobbling girder. At the last second, he was able to grab hold before falling.

"You just think about getting back up," he said.

But for the untrained onlooker, the feeling on this open-air roost is deep dread. The fear sinks in and shakes you.

"I was so scared," said Jennings of his first tall assignment. "I thought the floor boards were going to bust through."

Fright can grip a greenhorn so badly that three men have to crawl out on a beam after him to pry him loose.

"You got to be free," said Goodwin. "You can't be shakin'. You just concentrate on putting one foot ahead of the next and don't think about anything else."

"You can tell pretty quick the ones that won't make it," said Hale, a 33-year veteran with a chest built for two and timber-thick arms. "They ain't got the daredevil in 'em."

It's no secret that ironworkers are a hard-drinking bunch. It's also known among them that courage to walk the line between danger and death sometimes comes in liquid form.

"I've drunk as many as 10 shots with breakfast," boasts Hale. "It may take a shot or two . . . I've worked sick as a dog, but I do the job. Because I don't want anybody calling me a candy-ass."

Workers like Goodwin and Jennings will travel the country looking for the big jobs -- 50 hours' work a week at $13 an hour. Many take home well over $20,000 a year. In his heyday, said Hale, he roamed from New York to Alaska driving rivets in bridges 1,000 feet high and pipelines covered with frost.

Risk is the ironworker's thrill. Danger, they say, is half the reason for being there. "I'd like to work higher," said Jennings, who camps out in his van at the work site and dines on Safeway deli and the mandatory six-pack of beer. "The higher, the better."

"They are a different species," said Stephen Cooper, an Occupational Safety and Health Administration official and himself a former ironworker. "They feel they're the last of the Mohicans."

Ironworkers don't mind working in what Cooper calls a "gray area" of safety codes, an area he says is nearly impossible to regulate. In fact, the workers wouldn't have it any other way.

"It's something nobody else can do," said Hale, biting off his sentences as if they were sticks of beef jerky. "They ain't got the guts. You lay a beam crosswise through a building, you walk out there with pride. You do your best and you look good. That's the name of the game.

Thirty stories up, with a bag pack and ready to "boom," as traveling is called, a man can be sure of himself, say ironworkers, even if he can never be sure he'll make it down alive.

"Most of the ironworkers don't make it with their families," said Goodwin. "Especially if they're boomers. That's why it scares me to get married. It's going to be the most difficult for your old lady, just walkin' through the door. 'Cause she don't know if you're ever comin' back."