Thin Walled Beams (TWBs) can be modelled as three dimensional bodies, shell, folded plates or, as their shape seems to suggest, as one dimensional continua. In the last case it must be pointed out that, also in the framework of the linear elasticity, the Saint-Venant solutions can not apply, in most of the cases, to those structures. This essentially because, generally speaking, they do not obey the Saint-Venant principle. Starting from the beginning of the twentieth century, many effort have been made to generate handy and reliable one dimensional models for TWBs both in linear and nonlinear fields. These proposals are examined by considering the cases in which the starting point is a 3D body, a 2D (plate or shell) model, a direct 1D continuum. The most relevant features of the structural behaviour of TWBs are discussed and some results obtained by using 1D models both in linear and nonlinear analyses, are reported.