The soldiers who stand guard at the Tomb of the Unknown Soldier are hand picked and rigorously tested

'Each soldier must have strong military bearing, discipline, stamina and present an outstanding soldierly appearance. Each Sentinel must be able to flawlessly perform seven different types of walks, honors and ceremonies. They must retain vast amounts of knowledge concerning the Tomb, Arlington National Cemetery, the United States Army and their unit.'

They must be perfect citizens, retain honor, exist with integrity... etc. they are the example of the U.S. military.