Pilot check valves are used to block the cylinder in both directions. Flow is free in one direction and blocked in the reverse direction until pilot pressure is applied.

VBPDE-A先导式液压锁用于在进油、回油两个方向上锁住油缸。当先导油液没有施加在对侧方向的回路时，油液正向自由流动，反向截至，即为单向阀功能。当先导油液施加在对侧回路时，则正向、反向均可流动。