A rocker board is the most basic and least challenging type of balance board. It is a flat board with a attached to the board's underside. In some models the fulcrum is perpendicular to the board's length and in the other models the fulcrum is two rockers that are parallel to each other and parallel to the board's length, one in front of the person who is standing on the board and one behind. The ground-contacting edge of the fulcrum is curved in most models and is flat in some models.