Box springs are the mattress foundation that sits under most mattresses and functions both to absorb shock from movement and to elevate the mattress to a sitting position. Now rimmed with wood and covered in cloth, bed box springs are a much-needed upgrade to bedsprings. The wood perimeter of box springs give stability to your bed base, and the cloth cover keeps springs from harming your mattress. While it is not required for every mattress to have a box spring, most every mattress benefits from a solid bed.