Valves and Subplates For inline applications, use the 61642 Valve mounted on a 61646 Subplate. This set-up is also recommended for use with high volume air-powered hydraulic pumps in StayLock applications. For manifold mounting, directly on the pump, the 61647 Subplate and 61642 Valve are recommended. Because the Jergens Air-Powered Hydraulic Pump provides only the necessary hydraulic pressure to clamp and unclamp the StayLock Clamps, the Four-Way, Zero-Leakage Valve is recommended to prevent the unnecessary running of the pump, thus minimizing pump maintenance and wearout.