Abstract: A bracket structure is provided for attachment to the rock shaft of a draft implement and a swing arm having front and rear ends is pivotally attached at its front end to the bracket structure for oscillation of the swing arm relative to the bracket structure in a vertical plane about a horizontal transverse axis between a position with the swing arm generally horizontally disposed and a rearwardly and downwardly inclined position. Positioning and limit structure is operatively connected between the bracket structure and the swing arm limiting downward swinging of the arm relative to the bracket structure, allowing upward swinging of the rear end of the swing arm toward a horizontal position and including force structure yielding biasing the swing arm toward its limit of rearward downward inclination. The rear end of the swing arm includes a reversible smoothly laterally curving strap-type terminal end constructed of spring material.