Abstract: A water valve has a fixed valve housing, a knob pivotal on the housing about a knob axis and formed with a radially throughgoing aperture, and an abutment projecting radially from the housing. The aperture passes the abutment on rotation of the knob on the housing about the knob axis. A pivot on the knob defines a rocker axis adjacent the aperture and substantially parallel to but offset from the knob axis. A rocker pivotal on the pivot about the rocker axis has an end displaceable radially through the aperture between an inner position engageable with the abutment on movement of the window past the abutment and a position not engageable with the abutment on such movement. A spring braced between the rocker and the knob urges the rocker into the inner position.