Abstract: A cylinder valve includes a body with a threaded extension defining a first output port which screws directly into the cylinder port. An input port connected to a source of hydraulic fluid communicates with the first output port through an axially extending passage in a cylindrical valve spool. The passage also communicates with a second output port axially aligned with the first port and connected through a hose to a second cylinder which operates in unison with the first cylinder. A handle is provided for rotating the spool ninety degrees to block the ports and lock the cylinders against movement. The valve is particularly useful for locking the basket lift cylinders on a cotton harvester in the raised position for maintenance work.