An old-school rat rod is a custom car styled like early 1940s to 1960s hot rods. Rat rods are different from hot rods because rat rods are designed to exaggerate the style of the original hot rods.
Rat rods are designed to act as a counter-culture statement against traditional hot rods that convey a sense of upper-class style and elegance. Designers are encouraged to stylize and exercise artistic liberties with rat rods to create the desired effect. The term is sometimes used incorrectly to describe cars that are weathered or beaten, but correct rat rods only apply to hot rods designed to be over-the-top and grungy.