The invention relates to a device for shopping in a self-service store or for transporting luggage, comprising transport trolleys (30) which can be slid one into the other and at least one collection point for parking the transport trolleys (30). Said trolleys (30) are parked in at least two rows if there is only one collection point and in at least one row per collection point if there are at least two collection points. The device is for used exclusively in one particular area of application, for example a self-service store. Each transport trolley (30) is fitted with a coupling element (1, 1') which, by means of a plug-in element (13, 13') can be locked to and unlocked from a second transport trolley (30) in such a way that the trolleys (30) can be hired out against a deposit. The coupling elements (1, 1') comprise means that permit the formation of different types of coupling elements, so that only transport trolleys (30) fitted with the same type of coupling element (1, 1') can be locked to and unlocked from each other. One of said means is formed by a guiding element (9) which can be fitted to the coupling element (1, 1'), said guiding element having an opening (10) in the shape of the cross-section of the shaft of a plug-in element (13, 13'). In addition, the number of rows is identical to the number of different types of coupling elements (1, 1'), each row has a predetermined number of transport trolleys (30), and either the trolleys or coupling elements (1, 1') are marked with markings specific to each row. The invention provides for each guiding element (9) to be mounted to the coupling elements (1, 1') in only one predefined position and in such a way that it cannot be rotated, the number of different types of coupling elements (1, 1') corresponding to the number of different types of guiding elements (9).