RV Jargon


Gross Axle Weight (GAW) is the actual weight placed on a single axle.


Gross Axle Weight Rating (GAWR) is the maximum number that the GAW of a single axle should never exceed.


Gross Combination Weight (GCW) is the actual weight of the fully loaded tow vehicle plus the towed vehicle (trailer, car, boat, etc.), including all cargo, fluids, passengers, and optional equipment.


Gross Combination Weight Rating (GCWR) is the maximum number that the tow vehicle GVW plus towed vehicle GVW (or GTW) should never exceed.


A trailer and hitch configuration connected to the tow truck directly above the rear axle by way of a standard ball hitch in the truck bed and a vertical, slender arm on front of the trailer. Gooseneck hitching is common on horse and utility trailers, but rarely found on RV's.

Gooseneck Adapter (Extender)

A device that attaches to the fifth wheel trailer's king pin and extends down about two feet. It couples with a ball hitch mounted in the bed of a truck, enabling the fifth wheel to be towed like a gooseneck trailer. For additional details see Fifth Wheel Gooseneck Adapter.


The degree of inclination of a road. A grade of 6% or higher is considered steep.

Gray Tank

Holding tank connected to the sinks and shower, designed to hold waste water until it can be dumped into a septic system.

Gray Water

Waste water from the sinks and shower.


Gross Trailer Weight (GTW) is the same as Gross Vehicle Weight (GVW) when referring to a trailer.


Gross Vehicle Weight (GVW) is the actual weight of the fully loaded vehicle or trailer, including all cargo, fluids, passengers, and optional equipment, as measured by a scale.


Gross Vehicle Weight Rating (GVWR) is the maximum number that the GVW or GTW should never exceed.

Half Ton

Truck rating originally conceived to indicate cargo carrying capacity of a half-ton (1,000 lbs). Today, tonnage rating is no longer an accurate indication of cargo carrying capacity - it is more of a relational indication among trucks in different categories. Common one-ton pickup truck models are the Chevrolet 1500, Dodge 1500, Ford F-150, and GMC 1500.

Hauler Back

Truck body installed on a chassis in place of a bed, designed to tow or haul various loads. Most hauler backs look like a typical car wrecker without the lift. Hauler backs intended for RV towing have a flat surface and a hitch installed above the rear axle. Common options added to hauler backs are storage compartments and tool boxes.

Heavy Duty Truck

Commercial truck designed for heavy duty. Heavy trucks are suitable for towing the heaviest of trailers, though they are rarely used for RV towing. A few examples: semi trucks, Chevrolet Kodiak C8500, Ford F-750, GMC TopKick C8500. For additional details see Truck Classification.

Hitch Weight

Amount of a trailer's weight that rests on the tow vehicle; should be 10 to 15 percent with conventional trailers, 15 to 20 percent for fifth-wheels.

Holding Tanks

Tanks that hold the black (toilet) and gray (sink, shower, lavatory) water. Their capacity determines how long an RV can be used without hookups.

Honey Wagon

Euphemism for the sewage pumping truck. Honey wagons are used to empty RV holding tanks in places where full hookups and dump stations are not available.


Campground facilities for connecting an RV to 120-volt AC "shore power," water, sewer, cable TV and telephone service. Full Hookups: Refers to water, electricity and sewer at an RV site.

House Battery

One or more batteries in a recreational vehicle for operating the 12-volt lights, appliances, and systems. House batteries can be 12-volt units tied in parallel or pairs of 6 volt batteries tied in series (to double the voltage). The term house battery is of more significance in motor homes because they contain one or more other batteries for the operation of the engine, referred to as the chassis or starting batteries.


A device that converts direct current (DC) to alternating current (AC) for powering AC equipment while the RV is not plugged into an AC source. Typical DC sources are batteries and solar panels.


Abbreviation for Internet Service Provider.

Jake Brake (Exhaust Brake)

A device installed on the engine which causes deceleration by restricting the exhaust gases. Exhaust brakes are used to supplement the service brakes of a vehicle and to increase stopping power. Especially useful to slow heavy loads down steep grades.

King Pin

The pin by which a fifth wheel trailer attaches to the truck. It slides into the fifth wheel hitch and locks in place.

King Pin Weight (Pin Weight)

King Pin Weight (also called Pin Weight) is the actual weight pressing down on the fifth wheel hitch by the trailer. The recommended amount of King Pin Weight is 15%-25% of the GTW.


A sandwich of structural frame members, wall paneling, insulation and exterior covering, adhesive-bonded under pressure and/or heat to form the RV's walls, floor and/or roof.

Leveling Jack (Landing Gears, Landing Legs)

A jack lowered from the underside of trailers and motor homes for the purpose of leveling the vehicle. A leveling jack is designed to bear a significant portion of the RV's weight, even lifting it off the ground on certain models.

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