Okla. Stat. tit. 47, § 47-1-146: Pole trailer

Every vehicle without motive power designed to be drawn by

another vehicle and attached to the towing vehicle by means of a

reach or pole, or by being boomed or otherwise secured to the towing

vehicle, and ordinarily used for transporting long or irregularly

shaped loads such as poles, pipes or structural members capable,

generally, of sustaining themselves as beams between the supporting

connections.