1. In an implement having a frame adapted for connection to a tractor, transverse shaft means rockably mounted on the frame, laterally spaced wheel-carrying arms mounted on a shaft means, power-operated means mounted on a frame and having a connection with said shaft means for rocking the latter to swing said wheelcarrying arms vertically between positions corresponding to the operating and transport positions of the implement, an angular adjustment means operable independently of said power-operated means for angularly adjusting one of said wheel-carrying arms about the axis of said shaft means relative to the other of said wheel-carrying arms and holding said arms in a selected adjusted position to Level the implement, said shaft means including a pair of aligned wheel-carrying sections rockably mounted on the frame to which said wheelcarrying arms are secured and a lever secured to the inner end of each of said sections, means being provided for operatively connecting the power-operated means to said levers for rocking said wheel-carrying sections simultaneously, adjustable means forming the connection between the power-operated means in one of said levers to angularly adjust said one of said levers relative to the other and thereby vary the vertical positions of said wheel-carrying arms, and wherein a floating arm is mounted on the axis of said shaft means for pivoting relative thereto, pin means forming a connection between said levers and said floating arm, the connection of said pin means to said one of said levers including means for accommodating angular movement of said one of said levers relative to the other, and said adjustable means being connected between said one of said levers and said floating arm.