Method for designing a retrofitting device for retrofitting a receiving body for establishing compatibility with a suitcase for transporting transport goods, which suitcase is coupleable with another suitcase by coupling structures (30, 34, 38, 40, 44), wherein the method comprises: identifying coupling structures (30, 34, 38, 40, 44) of the suitcase which are required for establishing compatibility; manufacturing the retrofitting device with the coupling structures (30', 34', 38', 40', 44') which are mimicking the identified coupling structures (30, 34, 38, 40, 44); connecting the receiving body with the retrofitting device, such that the receiving body which is connected with the retrofitting device is coupleable with the suitcase by the coupling structures (30', 34', 38', 40', 44') of the retrofitting device and by the coupling structures (30, 34, 38, 40, 44) of the suitcase; wherein the retrofitting device is formed as a ledge profile; wherein the coupling structures (30, 34, 38, 40, 44) of the suitcase are configured such that the suitcase and another suitcase which comprises coupling structures (30, 34, 38, 40, 44) as further suitcase, by the coupling structures (30, 34, 38, 40, 44), on top of each other are selectively: vertically detachably stackable in a slide-secured manner; or vertically non-detachably coupleable with each other; wherein the coupling structures (30, 34, 38, 40, 44) of the suitcase are formed such that the suitcase and the other suitcase, by the coupling structures (30, 34, 38, 40, 44), in the state in which they are vertically non-detachably coupled with each other on top of each other, are selectively slidable with respect to each other; or by actuating the coupling structures (30, 34, 38, 40, 44) are slide-securable with respect to each other. identifying coupling structures (30, 34, 38, 40, 44) of the suitcase which are required for establishing compatibility; manufacturing the retrofitting device with the coupling structures (30', 34', 38', 40', 44') which are mimicking the identified coupling structures (30, 34, 38, 40, 44); connecting the receiving body with the retrofitting device, such that the receiving body which is connected with the retrofitting device is coupleable with the suitcase by the coupling structures (30', 34', 38', 40', 44') of the retrofitting device and by the coupling structures (30, 34, 38, 40, 44) of the suitcase; wherein the retrofitting device is formed as a ledge profile; wherein the coupling structures (30, 34, 38, 40, 44) of the suitcase are configured such that the suitcase and another suitcase which comprises coupling structures (30, 34, 38, 40, 44) as further suitcase, by the coupling structures (30, 34, 38, 40, 44), on top of each other are selectively: vertically detachably stackable in a slide-secured manner; or vertically non-detachably coupleable with each other; vertically detachably stackable in a slide-secured manner; or vertically non-detachably coupleable with each other; wherein the coupling structures (30, 34, 38, 40, 44) of the suitcase are formed such that the suitcase and the other suitcase, by the coupling structures (30, 34, 38, 40, 44), in the state in which they are vertically non-detachably coupled with each other on top of each other, are selectively slidable with respect to each other; or by actuating the coupling structures (30, 34, 38, 40, 44) are slide-securable with respect to each other. slidable with respect to each other; or by actuating the coupling structures (30, 34, 38, 40, 44) are slide-securable with respect to each other.