<Li> Turns and faces north for 21 seconds . </Li> <Li> Takes 21 steps down the mat . </Li> <Li> Repeats the routine until the soldier is relieved of duty at the changing of the guard . </Li> <P> After each turn, the Guard executes a sharp "shoulder - arms" movement to place the weapon on the shoulder closest to the visitors to signify that the Guard stands between the Tomb and any possible threat . </P>

What is the address of arlington national cemetery