On the street below, the weather is calm. But up here, high winds threaten to topple the workers. A sudden gust can knock them from their footing with its sheer force or send a fatal vibration through the beams on which they stand. And yet the men joke, laugh, stroll across the foot-wide beams as though they are on solid ground. To the people on the sidewalk, tiny as ants below, the skywalkers appear entirely unafraid. A hundred years ago, their grandfathers and great-grandfathers built the skyscrapers and bridges that surround them.