A joining-element (1) for mechanically joining switchgear-frames (2, 3) to one other, comprises a coupling-base-part (4) having a resting-surface (5) suitable for resting on, and coupling with a profile-rod (6) of a first switchgear-frame (2); a locking-mating-part (7) protruding from the coupling-base-part (4) and configured for mating with a further locking-mating-part of a further joining-element connectable to a respective profile-rod (6') of a second switchgear-frame (3), the locking-mating-part (7) having a through-opening (8) extending along an insertion-axis (9) and suitable for cooperating with a further through-opening of the further locking-mating-part for receiving a locking-pin-element (10) parallely to longitudinal-axes (11) of the profile-rods (6, 6'). The locking-mating-part (7) comprises a first aligning-surface-portion (12, 23) tilted with respect to the insertion-axis (9) and configured for enabling achievement of a mutual alignment position of the switchgear-frames (2, 3) according to a first direction (F1) parallel to the longitudinal axes (11), and of a desired relative side position according to a second direction (F2) orthogonal to the longitudinal axes (11) and to said resting-surface (5). On the locking-mating-part (7) and coupling-base-part (4) there is included a second aligning-surface-portion (13, 14) parallel to the insertion-axis (9) and sloping relative to the resting-surface (5), and configured for ensuring a reciprocal alignment of the two switchgear-frames (2, 3) according to a third direction (F3) orthogonal to the insertion-axis (9) and parallel to the resting-surface (5).