Abstract: A valve has a housing to which a 360 degree notch plate is integrally connected. A valve member mounted within the housing control fluid flows and rotates though substantially 90 degrees between maximally open and closed positions. A valve stem extends upwardly from the valve and through an opening formed in the notch plate. A handle is releasably secured to the valve stem immediately above the notch plate and has a spring-biased pivoting arm which cooperates with the notches to permit the angular position of the handle and consequently the valve member to be incrementally adjusted and locked. The upper surface of the notch plate has four distinct quadrants, and a number of holes formed at predetermined locations, a different pair of holes being associated with and positioned to either side of each quadrant. The valve stem is shaped to receive the handle in only predetermined angular orientations relative to the valve member.