A wing-type rotary mower apparatus with a hydraulically powered over-center self-locking wing lift that extends between the central mower deck and the wing mower deck(s) to effect wing movement from a working position to a locked transport position. The lift mechanism comprises a double acting cylinder, a bell crank, and a pair of lift links that are pivotally connected. When the cylinder is retracted the bell crank rotates inward towards the center of the apparatus transferring the movement through the lift links to the mower wing(s). The rotational force on the bell crank about a fixed central pivot point on the central mower deck goes from an outward force reacted to by the cylinder to an inward force supported by the stop seat on the central mower deck; effectively locking the wing(s). The procedure is reversed when the cylinder is extended to return the wing(s) to the working position.