Each year, the 3rd U.S. Infantry (The Old Guard) has honored America's fallen heroes by placing American flags before the gravestones and niches of service members buried at both Arlington National Cemetery and the U.S. Soldier's and Airmen's Home National Cemetery just prior to Memorial Day weekend.
During an approximately three-hour period, the soldiers place flags in front of more than 260,000 gravestones and about 7,300 niches at the cemetery's columbarium. Another 13,500 flags are placed at the Soldier's and Airmen's Cemetery. As part of this yearly memorial activity, Old Guard soldiers remain in the cemetery throughout the weekend, ensuring that a flag remains at each gravestone.
American flags are also placed at the graves of each of the three unknown service men interred at the Tomb of the Unknowns, by the Tomb Sentinels. All flags are removed after Memorial Day before each cemetery is opened to the public.
For a personal account of the "Flags In" ceremony and Memorial Day in Iraq, please read Badgers Forward - it is a beautiful piece.