The invention presents a system for assembling a box (1), comprising plates (3-6), each having, in the assembled condition of the box (1), an inner side and an outer side, and fittings (8, 9); each serving, in the assembled condition of the box (1), as a connection between at least two adjacent plates (3-6), and each comprising an inner fitting part (13, 13null) and an outer fitting part (12, 12null), to be placed at the inner side of the plates (3-6) and the outer side of the pates (3-6) respectively. In each fitting, the inner and the outer fitting parts (13, 13null, 12, 12null) are joined with each other by means of at least one bridge (14, 14null), the bridge (14, 14null) being positioned, in the assembled condition of the box (1), between at least two of the plates (3-6), between which the fitting (8, 9) serves as a connection.