The opening and closing element of a gate valve is the gate plate. The movement direction of the gate plate is perpendicular to the flow direction. The gate valve can only be fully opened or fully closed, and cannot be used for regulation or throttling. The gate plate has two sealing surfaces. The most commonly used type of gate valve has the two sealing surfaces forming a wedge shape, and the wedge angle varies depending on the valve parameters, usually 5°, and 2°52' when the medium temperature is not high. The gate plate of the wedge gate valve can be made as a single piece, called a rigid gate plate; or it can be made as a gate plate that can undergo slight deformation to improve its processability and compensate for the deviation of the sealing surface angle during processing. This type of gate plate is called an elastic gate plate. When the gate valve is closed, the sealing surface can rely solely on the medium pressure to seal, that is, the sealing surface of the gate plate is pressed against the other side of the valve seat by the medium pressure to ensure the sealing of the sealing surface. This is called self-sealing. 

Most gate valves are of the forced-sealing type, meaning that when the valve is closed, an external force is used to forcibly press the gate plate against the valve seat to ensure the sealing performance of the sealing surface. The gate plate of a gate valve moves linearly along with the valve stem. This type of gate valve is called a lift stem gate valve or a visible stem gate valve. Usually, there are trapezoidal threads on the lift stem, which convert the rotational motion at the top of the valve to a linear motion, that is, converting the operating torque into the operating thrust. When opening the valve, when the lift height of the gate plate is equal to the valve diameter in a 1:1 ratio, the fluid passage is completely unobstructed. However, during operation, this position cannot be monitored. In actual use, the top point of the valve stem is used as a reference, that is, the position where it cannot be opened further, as its fully open position. To account for the phenomenon of lock-up due to temperature changes, when the valve is fully opened to the top position, it is usually rotated back by 1/2 to 1 turn as the fully open valve position. Therefore, the fully open position of the valve is determined by the position of the gate plate, that is, the travel. Some gate valves have the valve stem nut on the gate plate, and the handwheel rotates to drive the valve stem to rotate, thereby lifting the gate plate. This type of valve is called a rotating stem gate valve or a concealed stem gate valve.