Shut-off valves start and stop the flow of compatible media within a system for maintenance, instrument installation, or to relieve system pressure. These valves are manually operated by a handle or handwheel, pneumatically actuated by compressed air, or activated by an electric motor. Ball valves use a bored-out rotary ball within the valve body to quickly start or stop media flow. Gate valves use a lever or handwheel to lower and raise the gate within the valve body. Diaphragm valves have isolated stems for controlling the flow of media containing suspended solids and slurries.