A modular lock valve holds the actuator exactly where the operator left it. Centre the directional valve and the pilot checks close; no spool leak, no drift.

Choose A or B where the load only ever acts one way, and A & B where it can act either way — outriggers, tilt cylinders, anything overcentre.

A modular lock valve sits at the valve bank, not at the cylinder. It will hold the load against spool leakage, but it cannot protect against a burst hose between the bank and the actuator. For overhead loads, fit a lock valve at the cylinder as well.

Modular valves stack. Each plate you add makes the assembly taller, so the mounting bolts must be longer — the bolt length in the table is what that single plate adds. Add up your stack and order the matching SHCS bolt set; they are not included.