Editing Truck (section)

===Frame===
[[File:A truck chassis section.jpg|thumb|A truck rear frame (chassis) section view]]
[[File:ToyotaTundraChassis.jpg|thumb|Pickup truck frame (right rear view)]]
A truck [[frame (vehicle)|frame]] consists of two parallel boxed (tubular) or C‑shaped rails, or beams, held together by [[crossmember]]s. These frames are referred to as [[ladder frame]]s due to their resemblance to a ladder if tipped on end. The rails consist of a tall vertical section (two if boxed) and two shorter horizontal flanges. The height of the vertical section provides opposition to vertical flex when weight is applied to the top of the frame (beam resistance). Though typically flat the whole length on heavy-duty trucks, the rails may sometimes be tapered or arched for clearance around the engine or over the axles. The holes in rails are used either for mounting vehicle components and running wires and hoses or measuring and adjusting the orientation of the rails at the factory or repair shop.

The frame is usually made of [[steel]], but can be made (whole or in part) of [[aluminum]] for a lighter weight. A [[Drawbar (haulage)|tow bar]] may be found attached at one or both ends, but heavy tractors almost always make use of a [[fifth wheel]] hitch.{{citation needed|date=November 2012}}<!-- One out of five heavy trucks (16 tonnes and above) in Sweden are tractors. http://www.vbg.se/sv/support/lfg_statistik/30.-Lastbilar_over_16_ton_1988-.pdf Virtually all other heavy trucks, the majority of the heavy trucks, have a bolt couplings (such as a [[Ringfeder]]). -->