A needle valve is a type of valve usually used in flow metering applications. It is similar in operation to a gate valve but tends to use a smaller, more precisely controllable orifice. When the handle is turned, a plunger slowly descends to block flow. The handle must be turned many times to open or close the valve; therefore, unlike a ball valve, it is impossible to tell from examining the handle position whether the valve is open or closed. A gate valve is a valve that opens by lifting a round or rectangular gate out of the path of the fluid. ... A ball valve (like the butterfly valve, one of a family of valves called quarter turn valves) is a valve that opens by turning a handle attached to a ball inside the valve. ...