In this chapter, the following terms have the meanings indicated. Terms Defined. “Chain attaching means” means a bolt, hook, pin, hole, eye, clevis, bracket, bar, or any other device mounted on and used for anchoring or attaching safety chains to the towed or towing vehicle or hitch. “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. “Gross vehicle weight rating (GVWR)” means the value specified by the vehicle manufacturer as the loaded weight of a single vehicle. Hitch. “Hitch” 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. “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 car structures or axles, when properly adjusted, distributes the imposed vertical load at the hitch and coupling connection between the structures or axles of towing vehicle and trailer. The towing vehicle thus loaded tends to retain a level position with respect to the road. “Weight-carrying hitch” means a mechanical 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. Weight-carrying hitches may be designed for bolting or other attachment to the towing vehicle frame, unitized body, bumper structure, or to a combination of these or other points which meet the requirements of Table 2 of Regulation .10 of this chapter. “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. “Manufactured” means the date that parts or components for devices regulated by this chapter are fabricated, assembled, packaged, or labelled, and in a saleable condition in the manufacturer's inventory of finished goods. “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 in a level position (detached from the hitch), and with trailer consumables and cargo in maximum loaded conditions. Primary Connecting System. “Primary connecting system” means the combination of devices and their attaching structures that are normally used to connect a towing vehicle and trailer during towing operations. “Primary connecting system” includes, but is not limited to, the ball and socket type of connection or the draft means of connection. “Primary connecting system” does not include a: Safety chain which is a part of a secondary system normally used only when the primary connecting system fails; or Weight distributing or sway control feature or device which functions as an accessory to the maintenance of the towing vehicle-trailer connection. “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, 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. “Tables 1, 2, 3, 4, and 5 and Figures 1, 2, 3, and 4” referred to in this chapter are contained in Regulation .10 of this chapter. “Trailer” means any towed vehicle having a registered gross vehicle weight rating of 10,000 pounds or less.