A bed is a piece of furniture used as a place to sleep or relax. It has a secondary use as a location to engage in sexual relations. Most modern beds consists of a mattress on a bed frame, with the mattress resting either on a solid base, often wooden slats, or a sprung base. In North America many beds include a box spring inner-sprung base, a large mattress-sized box containing wood and springs that provide additional support and suspension for the mattress.