Abstract: Underground water valves having square operating nuts, such as but not limited to critical water valves which control different pressure zones or different demand areas, are secured by a shielding cap, each of which have a recess that receives a valve operating nut and a cylindrical projection which frustrates attempts to rotate the operating nut. When an authorized person decides to open or close one of the valves, the shielding cap is retrieved from the operating nut by a retrieving head which has the socket defined by a frustoconical recess. Within the recess are a pair of opposed pins which seat in J-shaped slots in the frustoconical projection. Upon rotating the retrieving head, the pins move into alignment with open ends of the J-shaped slots, down shank portions of the slots and abut closed ends of the slots so that the shielding cap may be pulled from the valve operating nut and withdrawn through the valve operating box.