A box-spring is a bed base of wood and springs, covered in cloth. It is then placed on top of a metal bed frame which sits on the floor and braces the box spring. The box spring is usually the same size as the mattress which goes on top. The purpose of a box spring is to raise the height of the mattress, making it easier to get in and out of bed, as well as absorb shock and reduce wear on the mattress. A bed skirt is then placed on top of the box spring so that it covers the box spring as well as bed frame. A bed skirt hence makes a box spring less conspicuous. Bedskirts also cover the bed frame, which is made of metal or wood head, foot, and side rails and therefore may appear undesirable next to bedding. Most full size and up beds require a center bed rail, although a bed skirt is meant to cover the outer rails. The bed skirt has extended corners to cover the side rails, which can sometimes jut out. The 15” to 18” drop of the bed skirt is usually enough to cover both the box spring and bed frame, with the standard box spring between 5 and 9 inches thick and typical bed frame up to 9 inches tall. Box springs are covered in fabric and hence do not allow the bed skirt to touch the wood. Together with a box spring and bed frame, a bed skirt completes the raising of a mattress.