A hand-operated hydraulic jack rotatably mounted on a trailer to assist in removably attaching the trailer to the hitching mechanism of a towing vehicle. The jack can be rotated to a vertical position and hydraulically actuated with a hand-operated pump to lift or lower the trailer tongue relative to the hitching mechanism. Once the trailer is attached to the hitching mechanism or is otherwise being adequately supported, the jack can be retracted by opening a thumbscrew valve on the hydraulic circuiting body to allow the hydraulic fluid to move through the return circuit back to the hydraulic fluid reservoir in the jack. The jacks's actuator is retracted by means of springs at the sides of the jack. With the tongue of the trailer supported and the jack retracted, the jack may then be rotated to its horizontal position to provide maximum ground clearance.