So just what are they doing at the Capitol with those funny-looking, crooked-arm cranes and enough scaffolding to get a head start on a climb to the top of the dome?

The simple answer is that the Capitol's historic but deteriorating West Front is being restored. Workers are stuffing more than a mile of stainless steel rods into the walls of the Capitol to secure them for decades to come and replacing chipped and cracked stone carvings and damaged blocks of stone that cover the Capitol's facade.

It's projected to cost taxpayers $49 million and the scaffolding enveloping much of the West Front will not come down until the work is completed, which may not be until October 1988.

When it is done, Architect of the Capitol George M. White said, the Capitol "will look exactly like it did when it was new, but it will be structurally sound for the foreseeable future."

Hidden in the simplicity of the work, however, are complexities that perhaps can be appreciated only by those who revel in the intricacies of history and the need for precision in maintaining the heritage of the nation's seat of government.

When the West Front was built in the 1820s, numerous stone carvers and masons worked on the project and may have thought they were building the sandstone pilasters, columns and the intricate carvings atop them exactly alike.

But they did not. Carvings that to the untrained eye look the same may have leaves curled in opposite directions or be smaller than those atop adjoining pillars. White's goal is to restore such 160-year-old work to "exactly the way it was before." Or as Joe Downing, the superintendent for the Charles H. Tompkins Co., the general contractor for the restoration, said, "They even want us to duplicate the mistakes."

To accomplish that, workers are slathering a rubberized compound onto the carvings, which then is peeled off to create a mold. Plaster casts are subsequently made of the carvings and shipped to the Bybee Stone Co. in the tiny southern Indiana hamlet of Ellettsville.

There, Wilbur Bybee, the firm's president, said five limestone carvers, guided by their own vision of the plaster molds, are chiseling new Capitol carvings with pneumatic hammers. Another nine stonecutters are working on more uniform pieces that are less intricate.

Bybee also is supplying cut blocks of stone for construction at the Washington Cathedral and the Smithsonian Institution. But he said the Capitol work is much more exacting because "there's no two of the carvings alike and they're insisting we make 'em just like they were."

Still, he said White's office has yet to give the firm final marching orders on whether every column has to be recreated exactly as it was built.

"Now, can you tell if a column is an eighth of an inch too wide when you're looking up 80 feet?" he asked. "We don't care how we do it, just so someone makes a decision. That's the hardest place in the world to get anyone to make a decision."

The restoration was approved by Congress two years ago after a two-decade-long dispute over whether to restore the West Front or extend it, as White and some congressional supporters wanted to do.

"My position was that the design of the building was incomplete," White said, "because when that big dome was completed in the 1860s, then-Architect of the Capitol Thomas Walter said both the East and West fronts should be extended." The East Front was extended in the 1950s.

Few people on Capitol Hill will be able to see any of the West Front work up close, however, unless they happen to work in, or visit, an office that peers into the scaffolding. Large barricades surrounding the construction staging area have been erected beneath the West Front and security is tight. The construction workers have to pass through metal detectors as they enter the job site.

Under the restoration, construction crews first chemically removed 30 to 35 coats of white paint that had been brushed onto the West Front's sandstone exterior over the years, giving the facade a natural, slightly brownish hue for the moment.

Now, crews are removing the damaged carvings and blocks of facade stone, drilling small holes into the Capitol's walls and inserting 6,777 feet of stainless steel rods in lengths of 2 feet to 38 feet. Downing said grout is being shot into the holes, which are pinpointed on elaborate architectural blueprints, while the rods are anchored in epoxy and held at both ends by metal plates.

"The thinking is that the grout will seep into the cracks inside the stone blocks and make them stronger," Downing said. The metal plates are then covered with the cut blocks of Indiana limestone.

The unusual, crooked-arm cranes -- only four exist in the country -- are being used to hoist the stonework into place, Downing said, out of fear that a crane operator might accidentally swing a conventional boom smack into the side of the Capitol dome. The hooked cranes have special safety catches that limit the arc in which they can be operated, to ensure that the dome is not smashed.

Eventually, White said the West Front will be covered with a special white paint, "to permit moisture in and out of the wall, to permit the wall to breathe, so to speak, and at the same time preserve the stone on the wall." In addition, the West Front's rotting wooden windows are being replaced.

As White said of the work, "It's uncomplicated, but it needs to be meticulously done."