screw clamp [OFr, escroe, screw; AS, clam, fastener] , a device, usually made of plastic, equipped with a screw that can be manipulated to close and open the primary IV tubing for regulating the flow of IV solution. Turning the screw clockwise closes the tubing; turning it counterclockwise opens it. Different positions of the screw between the open and the closed positions allow the IV fluid to flow at different rates. Compare roller clamp, slide clamp.
