The Tomb Guard marches 21 steps down the black mat behind the Tomb, turns, faces east for 21 seconds, turns and faces north for 21 seconds, then takes 21 steps down the mat and repeats the process. After the turn, the sentinel executes a sharp "shoulder-arms" movement to place the weapon on the shoulder closest to the visitors to signify that the sentinel stands between the Tomb and any possible threat. Twenty-one was chosen because it symbolizes the highest military honor that can be bestowed -- the 21-gun salute.