There is no better illustration of the point than this photograph. Today, in the middle of Hurricane Irene, a young soldier walked his tour at the Tomb of the Unknown Soldier at Arlington National Cemetery.
While on duty the Tomb Sentinel crosses a 63-foot rubber surfaced walkway in exactly 21 steps. He then faces the Tomb for 21 seconds, turns again, and pauses an additional 21 seconds before retracing his steps.
The 21 is symbolic of the highest salute according to dignitaries in military and state ceremonies.
Members of The Old Guard have guarded the Tomb every second, of every day regardless of weather or holidays since April 6, 1948.