Portal frames can be defined as two-dimensional rigid frames that have the basic characteristics of a rigid joint between column and beam. The main objective of this form of design is to reduce bending moment in the beam, which allows the frame to act as one structural unit.

Ladder frame chassis is one of the oldest types of chassis. It is still used today for some off-road and commercial vehicles. Such a structure consists of two long beams that are supported by further shorter beams.