A structure for a cabinet containing electrical materials is disclosed having posts, crossbeams and connecting means. The connecting means are adapted to join one to another at least two crossbeams and one post, and including a base element and a hollow element which is provided with a substantially axial opening. The base element is constrained to the crossbeams and has an inserting portion adapted to be inserted inside the hollow element. Conversely, the hollow element is adapted to be constrained to the post. In particular, the hollow element, the post and the inserting portion are each provided with a bore, the bores being alignable one to another in operative conditions. A joining element provided with a truncated—cone shaped portion is adapted to pass in each of the bores when they are aligned, so that to constrain one to another the hollow element, the post and the inserting portion.