Float and thermostatic traps (F&T) are used for draining steam equipment and as drip traps. As the name implies, F&T traps are a combination of two separate devices, a float trap and a thermostatic vent. It consists of a chamber with a discharge valve at the bottom; the valve is actuated by a float and lever. The float is usually spherical in shape to resist the pressure of the steam. The thermostatic vent remains open until the trap heats up; it vents allow a large amount of air to pass. A variation of the F&T trap has been called a variable orifice trap; this trap has a free-floating float that acts as the closing mechanism.