Suddenly the wind came up, and the four glaziers walking cat-like atop the Old Post Office Building joked about being blown away as they carried sheets of mirrored glass up the steep slope of the massive skylight.

Working and walking as a team, they lowered the glass into place, secured it and returned for another. It is slow, methodical and dangerous work. With good weather and no accidents, they expect to have the entire roof glassed over by Nov. 1.

The new skylight, about a half-acre of glass that replaces a metal roof, is part of a $16 million renovation and restoration of the tallest office building in Washington -- and one of the most controversial.

An awkward, ugly structure to some, an architectural treasure to others, the 80-year-old Old Post Office Building has had its critics -- both inside and outside its doors -- for years. Threatened with demolition since 1928, it survived a death sentence delivered in 1968, and will be reborn in the 1980s as a federal office building with commercial shops and restaurants on the lower floors.

The building at Pennsylvania Avenue and 12th Street NW was completed in 1899 after seven years of work under the supervision of five different architects.

The nine-story granite structure is a somewhat jarring symphony of arches, pointed dormers, turrets and columns, with a 315-foot clock tower over the front door. The building, nicknamed "The Tooth" because of its tower, is nearly 28 feet taller than the Capitol down the street, though the Capitol appears taller because of its hill.

The 18,000-square-foot interior court-yard is surrounded by nine stories of gracefully arched balconies. When it was built, however, a glass celing was put over the mail room on the first floor, which meant workers on higher floors could look down into the courtyard, but couldn't stand in the middle of it to look up at the skylight.

The building, which at one time housed the entire postal system for Washington, saw the birth of parcel post, postal insurance, C.O.D. and special handling.

It became a favorite spot for parade-watching, beginning with President McKinley's inaugural parade in 1901.

And Flag Day -- June 14 -- was also a special occasion. Each year employes draped the building inside and out with flags, including one that stretched seven stories down from the skylight. A wooden platform was set up on the first floor's glass ceiling and an orchestra played patriotic songs for the employes above.

But "The Tooth" has had its share of critics. Early press reports called it "lavish" and "extravagant." Even before it was completed, the taste for ornate, Romanesque-style buildings had shifted toward smaller structures with simpler lines. By the time the nine surrounding Federal Triangle buildings were completed in 1938, there were calls for the postal building to be demolished. It had never been included in the "grand plan" of the Triangle and now stood out like an eyesore next to its lower, more understated neighbors.

Those who had to work inside the building didn't like it much either. The glass skylight brought in the sun, but it also let in heat in summer, cold in winter and rain all year round.

The government didn't get around to fixing it until 1931. The solution: replacing the glass roof with a metal one. Now the atrium was cast into darkness and gloom and the workers had a new name for the building: "The Pit."

In 1968, the National Capital Planning Commission, which is responsible for the preservation of government buildings, voted to demolish the postal building and complete the Federal Triangle as originally planned.

But the building suddenly found itself a vocal fan club. A group of citizens, who came to be known as Don't Tear It Down, rallied to save the building. Seven years later the planning commission reversed its decision.

A design competition was held to determine the future of the building, and in 1977, Washington architect Arthus Cotton Moore won with a plan for a mix of federal offices, restaurants and shops.

Moore, who says the building looks like a "monument to a prehistoric civilization," sees the renovated structure as a bridge between the tourist areas of the Mall and the old downtown area.

"We want to attract Mr. and Mrs. America who visit the Mall to this part of town," Moore said. "We want them to experience the atrium and the skylight, to see the quality of the architecture . . . The elevator ride to the top of the tower will give them the best view of Washington."

In addition to a shopping arcade, the building will house federal agencies concerned with the arts, humanities and historic preservation. The mix of commercial and government activities is permitted under a recent federal law.

The renovation of the building has turned up some surprises -- a store of old, empty liquor bottles in hideaway places and mounds of pigeon droppings, as high as 3 feet in some places.

Work was shut down in the tower and on some turrets this past June when the droppings were found to contain a fungus that can cause meningitis.

"Large amounts of pigeon droppings in an enclosed area are a potential problem once they're disturbed," said Peter Gillson, a General Services Administration safety supervisor. "We are being cautious and we are carefully removing the droppings."

It took seven years to construct the building and it will take four years to renovate it -- if the work stays on schedule.

Charles Turrisi, one of the glaziers on the roof, is looking forward to that day.

"It's a beautiful figure of a building," he said. "And when it's finished, people are going to come in here to that restaurant they're planning and they're going to look up through this skylight and they're going to wonder how we did it."

"You know that architect (Moore) designed the building, but we're the guys who build it," said Jack Scully, a sheet-metal worker helping out on the roof. "When they put a plaque up when it's all finished, our names should go on it. Our hands are upon this building."