At 3 a.m. Arlington Cemetery would be completely quiet but for the sharp click of heels - the Tomb guard. He stands alone, surrounded by 166,000 dead Americans, three of whome received his special attention.

At night, the guard moves in a circle, rather than the straight lines followed so religiously during the day. Meanwhile, fifty yards away, in an airconditioned, bunker-style barracks, six off-duty guards sleep, eat, watch television, iron uniforms and spit-shine shoes. Some of them are still teenagers, but the sergeants tell stories of Vietnam and anti-war demonstrations.

These men are the elite of the Old Guard Battalion, the only unit in the United States Army authorized to pass in review carrying fixed bayonets.

They are tall, straight and broad-shouldered. But this appearance is not entirely natural. Beneath the perfect military bearing lie the tricks of the trade.

Surgical corsets or masking tape keep even the most muscular stomachs a little sleeker. Screwdrivers are used to force shoe laces from sight. To dress, or "blouse" for guard duty is a fifteen-minute, two-man ritual - never hurried, never flawed, day or night.

At night the only visitor is an occasional office who comes by to dispense swift punishment for even the most minor infraction of proper conduct or appearance. But it takes more than that to motivate a solitary man to march unnoticed in the dead of night in perfect uniform and perfect step, no matter what the weather or the hour.

What do they think about while they're out there? The question hits a guard in the middle of the night just after he's come off duty. His face shows no room for deceit.

"I'm counting to myself, twenty-six, twenty-seven, twenty-eight, turn," he says. "And I'm thinking about him in the tomb and wondering if he knows I'm here."

Men don't tell lies at 3 a.m. in Arlington Cemetery.