A backbone chassis is a type of automotive construction with chassis, that is similar to the body-on-frame design. Instead of a relatively flat, ladder-like structure with two longitudinal, parallel frame-rails, it consists of a singular central, strong tubular backbone (usually rectangular in cross-section), that carries the power-train, and connects front and rear suspension attachment structures. Although the backbone is frequently drawn upward into, and mostly "above" the floor of the vehicle, the body is still placed on or over (sometimes straddling) this structure from above.