The cartridge lock valves combine a Kepsel® Cartridge Insert Check with a rugged pilot operator, and function the same as the counterpart Kep-O-Lok® inline lock valve. They free flow from valve port to cylinder port (or portion of circuit) and “lock” reverse flow until pilot pressure is applied to unlock the internal check valve and allow reverse flow. Kepner's Flexible Seal Seat™ provides positive bubbletight locking to prevent load drift or circuit creep, and answers the need where internal leakage could adversely affect performance such as with clamping cylinders or outrigger stabilizer jacks. Standard and specialty valve designs handle a wide variety of block and load hold applications, and are ideal for use in manifolds, subplates, or cylinder heads.