Flat sheet piles work differently from other sheet piles. Most sheet piles rely on their bending strength and stiffness to retain the soil or water. Flat sheet piles are formed in circles and arcs to create gravity cells. The cells are held together through the tensile strength of the interlock. The tensile strength of the lock and the allowable rotation of the lock are the two main design characteristics. The flat sheet pile cells can be made to huge diameters and heights and withstand a great deal of pressure.