The Rexroth Z2S 6-1-66/ is a pilot-operated check valve of sandwich plate design, engineered for reliable performance in modular hydraulic systems. It is designed to be stacked between a directional valve and a subplate or manifold block, conforming to the ISO 4401 (NG6 / CETOP 03) standard. This valve provides leak-free blocking of flow in one direction (from A2 to A1) while allowing free flow in the opposite direction (from A1 to A2). The blocked flow can be opened by applying pilot pressure to the opposite line (port B2), making it ideal for applications that require holding a hydraulic actuator in position, such as preventing cylinder creep under load.