An apparatus for positively locking the wheels of a disc in transport and depth control positions. The disc harrow comprises a frame having disc sections secured thereto. A transversely extending axle is secured to the frame and has ground engaging wheels at the opposite ends thereof which control the discing depth and transport height. A hydraulic cylinder is secured at its forward base end to the frame and has the rearward end of its cylinder rod pivotally connected to the axle to raise and lower the wheels with respect to the frame. A spacer assembly slidably embraces the cylinder rod. A cylinder stroke lock assembly is pivotally connected, at its rearward end, to the rearward end of the cylinder rod for pivotal movement between a first horizontal position and a second upstanding position. The spacer assembly comprises a spacer tube and spacing washers. The spacing washers may be selectively moved with respect to the cylinder stroke lock assembly to permit depth control adjustment. The cylinder str
