The Stomp Dance Grounds contain an elevated square platform with the flat edges of the square facing the cardinal directions. This is formally referred to as the Square Ground, which is incircled by a ring-mound of earth. In the center of this is the ceremonial fire, which is referred to by many names including 'Grandfather' fire. Ceremonially, this fire is the focus of the songs and prayers of the people and is considered to be a living sacred being. Stomp Dance participants include a leader, assistants, and one or more female shell shakers who wear leg rattles traditionally made out of turtle shells filled with pebbles. Some wear shakers made from small milk cans. The shakers provide rhythmic accompaniment while dancing around the fire, and a dance cannot begin without the shakers. As the dance progresses, as many as several hundred people may join the circle. The dance continues until at least four rounds or four songs are completed by the dance leader.