The floating seat allows bi-directional use, quick and easy field repair and low torque for opening/closing. The one-piece precision-machined floating slab gate utilizes floating seats that co-opt line pressure to supply the sealing force. Excessive force is not required for closing and sealing and smooth operation can be assured during extreme thermal cycles. Selective Backseat provides unparalleled safety during venting, lubrication, allows stem packing replacement without removing valve from service. A routine maintenance program keeps repairs to a minimum, and vital valve components may be replaced when necessary without the use of special tools.