A screen valve (210) to control fluid flow comprising at least one multi-apertured valve plate (220) movable laterally relative to a multi-apertured valve seat (230) between a closed configuration whereby the apertures are not registered to prevent fluid flow, and an open configuration whereby the apertures are registered to permit fluid flow, wherein the valve plate is supported by a multi-apertured carrier plate (240) that moves laterally in synchrony with the valve plate (220) to maintain a predetermined lateral registration between their respective apertures as the valve plate moves between the open and closed configurations, the valve plate being movable relative to the carrier plate so as to be able to lift off and return into contact with the valve seat. The co-moving carrier plate shields the valve plate so as to minimize pressure locking. Aerodynamic features may be incorporated to urge the valve plate (220) towards or away from the carrier plate (240).