Abstract: The section has a tubular shape with a substantially polygonal cross-section, provided with two larger faces (1, 2) opposite to one another and two smaller faces (3, 4) forming a connection with said larger faces, which extend in abutment elements (5, 6) suitable for defining with said larger faces the inner front and the outer front, respectively, of the window or door frame. The two larger faces (1, 2) comprise respective central portions (11, 12) parallel to one another provided with flaps (13, 14) defining C-shaped cavities (15, 16) for housing and connecting various members of the window or door frame. Each larger face also comprise lateral portions (17, 19; 18, 20) converging towards the corresponding lateral portions of the other larger face until they connect with the smaller faces. The section includes a hole (21) for drainage purposes.