These rugged valves combine two Kepsel® Cartridge Check Valves with close fitting pilot piston shuttle to offer dependable cylinder locking in both directions. They permit free flow from valve port to cylinder port (or to portion of circuit) through one check valve while at the same time piloting open the check valve on the other side to allow reverse flow. When pressure at the valve ports is removed both check valves close and lock against movement in either direction by preventing reverse flow. Kepner's Flexible Seal Seat™ provides positive bubble-tight locking to prevent load drift or circuit creep. Standard and specialty valve designs handle a wide variety of applications, and are commonly used with double acting cylinders for position locking and for holding against line rupture or control valve leakage.