A height of cut adjustment mechanism is provided for a rotary cutting deck mounted on a lift arm extending from a traction vehicle. The mechanism includes a front axle and a rear axle, at least one roller mounted on each axle, and a pair of height of cut arms extending from each axle to a pivot axis on the rotary cutting deck. A notch lock on each height of cut arm may be moved between a locked position in which the notch lock engages a notch plate at a desired cutting height, and an unlocked position in which the notch lock disengages the notch plate so that the height of cut arm can pivot with respect to the rotary cutting deck. A lever attached to each notch lock can be operated to move the notch lock between the locked and the unlocked positions.