Abstract: A baler adapted for towing by a tractor to pick up a windrow of hay and roll the hay into a cylindrical bale of substantial size and weight. The baler includes a gate pivotable rearwardly and upwardly to permit discharge of a completed bale onto the ground behind the baler. The gate is raised and lowered through a hydraulic system powered from the tractor. The hydraulic system includes a pair of hydraulic cylinders connected to the gate to raise and lower it upon extension and retraction respectively of the cylinders. This action is controlled by a manual flow control valve accessible to the operator on the tractor. The hydraulic system further includes a manual selector valve accessible on the baler to hydraulically lock the cylinders in their extended position to thus lock the gate in its raised position when desired.