Compositional technique used to determine the "ideal" position of the main subject in the frame. It is based on creating a rectangle from a square. A line drawn from the centre of one side of the square to the opposite corner becomes the radius of an arc. The side of the square is then protracted until it meets the arc, and from this point a rectangle is constructed. The side of the square which remains in the rectangle indicates the point at which the subject should be placed.