A one-piece, single-material seal (50A, 50B) for a double-panel electrical cabinet, intended to seal a junction between an enclosure, a back panel and a front panel of the electrical cabinet, comprising: - a positioning base, comprising: ∘ a base in the form of a non-circular straight cylinder extending along a vertical axis, an internal surface of the base being concave, the base being configured to be attached to a rabbet of the back panel of the cabinet, so that the base mates in a form-fitting manner with a convex part of the rabbet, and ∘ a tenon, comprising two positioning wedges (58A, 58B) extending parallel to each other in two longitudinal planes (πA, πB) parallel to the vertical axis, and a groove formed between the two positioning wedges, the groove being configured to receive an edge of a notch formed in a flange of the back panel, the groove being configured so that its shape fits a shape of the notch; and - an elongate guide, extending along a horizontal axis perpendicular to the vertical axis and to the longitudinal planes (πA, πB) and passing through the tenon, and forming a groove configured to receive a channel of the enclosure, the channel bearing against the elongate guide, so as to position the seal (50A, 50B) along the vertical axis relative to the channel, and so as to provide impermeability between the seal and the channel. - a positioning base, comprising: ∘ a base in the form of a non-circular straight cylinder extending along a vertical axis, an internal surface of the base being concave, the base being configured to be attached to a rabbet of the back panel of the cabinet, so that the base mates in a form-fitting manner with a convex part of the rabbet, and ∘ a tenon, comprising two positioning wedges (58A, 58B) extending parallel to each other in two longitudinal planes (πA, πB) parallel to the vertical axis, and a groove formed between the two positioning wedges, the groove being configured to receive an edge of a notch formed in a flange of the back panel, the groove being configured so that its shape fits a shape of the notch; and ∘ a base in the form of a non-circular straight cylinder extending along a vertical axis, an internal surface of the base being concave, the base being configured to be attached to a rabbet of the back panel of the cabinet, so that the base mates in a form-fitting manner with a convex part of the rabbet, and ∘ a tenon, comprising two positioning wedges (58A, 58B) extending parallel to each other in two longitudinal planes (πA, πB) parallel to the vertical axis, and a groove formed between the two positioning wedges, the groove being configured to receive an edge of a notch formed in a flange of the back panel, the groove being configured so that its shape fits a shape of the notch; and - an elongate guide, extending along a horizontal axis perpendicular to the vertical axis and to the longitudinal planes (πA, πB) and passing through the tenon, and forming a groove configured to receive a channel of the enclosure, the channel bearing against the elongate guide, so as to position the seal (50A, 50B) along the vertical axis relative to the channel, and so as to provide impermeability between the seal and the channel.