The MAGNUM is designed for only full-size pick-up trucks. To start with, there is no truth to the urban myth that Gross Trailer Weight (GTW) was once measured in units of 300 pounds called WHTs, in honor of William Howard Taft, our heftiest unknown president. Gross Trailer Weight is the weight of the trailer completely loaded. To determine actual GTW, you'll need to put your trailer on a vehicle scale. Tongue weight (TW) is the downward force placed on the hitch ball by the trailer coupler. Usually, TW is 10% to 15% of GTW. You can measure Tongue weight with a bathroom scale. Rest the trailer coupler on the scale and position the scale on a box so that the trailer is at normal towing height. Load the trailer as if it were being towed. Note that the tow vehicle's maximum towing capacity can be found in the owner's manual.