A 180.degree. folding tool bar for an agricultural implement is described including a main frame having wing sections pivotally mounted on the ends of the main frame which are movable between field and transport positions. A hydraulic cylinder is positioned within the main frame at each end thereof and has one end connected to the main frame. The rod end of each of the hydraulic cylinders is connected to one end of a wheeled carriage with the other end of the wheeled carriage being pivotally connected to the inner end portion of the associated wing section. The inner end of the carriage has a horizontally disposed slot which receives the rod end of the hyraulic cylinder to enable the wing section to float relative to the main frame when in the field position. A locking mechanism is provided on the carriage for locking the rod end of the hydraulic cylinder at the outer end of the horizontal slot as the hydraulic cylinder is operated to move the wing section between its field and transport positions thereby preventing undesirable free fall of the wing section during the movement of the wing section between its field and transport positions and vice versa.