Minn. Stat. § 169.43: SWINGING GATE ON TRUCK.

(a) No truck shall be operated on any highway with gate, loading rack, or partition carried in any manner on any part of the exterior of the truck, unless the top and bottom of such gate, loading rack or partition is securely attached to the truck, so as to prevent swinging or becoming loose.

(b) No truck shall be driven or parked on any highway with tailgate or tailboard hanging down or projecting from the vehicle except while such vehicle is being loaded or unloaded, and except when a load on the tailboard renders impossible the closing of the tailboard.