Many vehicles come with factory bars (usually the flat oblong shaped ones) and these can work fine to transport your kayak and can usually be fitted with most kayak carriers, but they lack the carrying capacity and long term strength of a good after-market rack system. If you are planning to transport a motorcycle in your truck or trailer to go to a racing or exhibition venue, then you would need a motorcycle ramp (also referred to as a motorcycle loading ramp or ATV ramp). Motorcycle loading ramps are made with metal, often aluminum. Loading Bars: Thule as well other companies make a bar that extends out so you can lift one end of the kayak on the bar and then lift the other side onto your rack. A popular way to transport two kayaks with a factory system is to transport one in a J-type carrier and the other flat or face down on the bars. Most SUV's come with factory racks that work well to receive most kayak carriers and transport accessories. The shorter the distance between the straps/bars the less secure the system will be. Always, use bow and stern lines when transporting by car or any vehicle with a short roof span - a favorite of ours is the Thule Quickdraw. Also, if you are going to transport 2 kayaks, cradles do limit the usable space on your rack bars. These types of racks offer the most weight capacity and are the safest way to transport kayaks on a vehicle.