(1) "Coupling" means that part of the primary connecting system normally mounted on the trailer, such as a socket, by which the connection is actually made and including the supporting attachment to the trailer frame.

(2) "Gross vehicle weight rating (GVWR)" means the value specified by the vehicle manufacturer as the loaded weight of a single vehicle.

(3) "Hitch," defined for specific uses under (a) and (b) of this subsection, means that part of the primary connecting system normally mounted on the towing vehicle, including a ball-support platform and those components which are attached to the towing vehicle.

(a) "Weight distributing hitch" means a mechanical device that connects the trailer to the towing vehicle, and by means of a leverage applied on both trailer and vehicle structures, when properly adjusted, distributes the imposed vertical load at the hitch and coupling connection between the structures of axles of towing vehicle and trailer.

(b) "Weight carrying hitch" means a mechanical and/or structural device that connects the trailer to the towing vehicle, and that does not employ features designed to redistribute the load imposed at the hitch and coupling connection.

(4) "Maximum gross trailer weight (MGTW)" means the weight of the trailer plus the weight of all cargo, consumables, and equipment loaded on the trailer when in an actual underway towing condition.

(5) "Maximum vertical load on hitch (tongue weight)" means the vertical downward static force exerted on the hitch by the coupling at the point of connection of coupling and hitch, with weight distribution features or devices, if any, deactivated. Tongue weight is measured at the trailer coupling, with the trailer on a level surface (detached from the hitch), and with trailer consumables and cargo in maximum loaded conditions.

(6) "Patrol" means Washington state patrol as defined in chapter 43.43 RCW.

(7) "Primary connecting system" means the combination of devices and their attaching structures that are normally utilized to maintain the connection between towing vehicle and trailer during towing operations. This includes, but is not limited to, the ball-and-socket type of connection or draft means. Note: This does not include a safety chain, which is part of a secondary system normally utilized only upon failure of the primary connection, nor does it include weight distributing or sway control features or devices whose function is accessory to the maintenance of the towing vehicle-trailer connection.

(8) "Safety chains" means flexible tension members connected from the front portion of the towed vehicle to the rear portion of the towing vehicle for the purpose of retaining connection between towed and towing vehicle in the event of failure of the connection provided by the primary connecting system. The term "safety chains" includes not only chains, cable, or wire ropes, or equivalent flexible member meeting the strength requirements of SAE J684 revised July 2005, but also any splice, clamp, socket, snap, eye, ring, thimble, pin, or other fastening device or forming method which is part of the assembly of any such flexible tension member.

(9) "Responsible manufacturer" means that person who manufactures a hitch or hitch component either for resale or for sale where it is not actually installed by the manufacturer.