Adapter as a fastening and contact-making device for an electronic domestic meter (eHZ) which has respectively projecting contact tongues and fastening feet, - having a connecting apparatus which blocks unauthorized access to the access and outgoing lines of the adapter and is secured by a lead seal, - having a mechanical locking apparatus for an eHZ which is seated with contact on the adapter, - wherein the mating contacts of the adapter for the contact tongues of the eHZ are designed solely as plug-in contacts such that a contact-connection between them can be produced solely by movement of the contact tongues into the mating contacts in one direction, - wherein the operating apparatus for the locking apparatus is present beneath the cover of the connecting apparatus, which cover is protected by a lead seal, - characterized in that - the locking apparatus has a sliding element, which can be moved back and forth, in the form of a sliding plate, - the sliding plate can be slid into a position between at least one of the fastening feet of an eHZ such that at least this foot is present in a fixed position on the adapter, - the sliding plate is designed in the form of a frame such that it frames the contact-making region between an eHZ and the adapter, - the sliding plate has a left-hand-side and right-hand-side plate web (36, 38), which two plate webs are fixedly connected to one another at their upper and lower end by an upper and, respectively, a lower transverse web (32, 34), - a grip is present on the lower transverse web, the sliding plate protruding into the region of the connecting apparatus by way of the said grip and the said grip being present beneath the lead-sealable cover of the connecting apparatus. - having a connecting apparatus which blocks unauthorized access to the access and outgoing lines of the adapter and is secured by a lead seal, - having a mechanical locking apparatus for an eHZ which is seated with contact on the adapter, - wherein the mating contacts of the adapter for the contact tongues of the eHZ are designed solely as plug-in contacts such that a contact-connection between them can be produced solely by movement of the contact tongues into the mating contacts in one direction, - wherein the operating apparatus for the locking apparatus is present beneath the cover of the connecting apparatus, which cover is protected by a lead seal, - characterized in that - the locking apparatus has a sliding element, which can be moved back and forth, in the form of a sliding plate, - the sliding plate can be slid into a position between at least one of the fastening feet of an eHZ such that at least this foot is present in a fixed position on the adapter, - the sliding plate is designed in the form of a frame such that it frames the contact-making region between an eHZ and the adapter, - the sliding plate has a left-hand-side and right-hand-side plate web (36, 38), which two plate webs are fixedly connected to one another at their upper and lower end by an upper and, respectively, a lower transverse web (32, 34), - a grip is present on the lower transverse web, the sliding plate protruding into the region of the connecting apparatus by way of the said grip and the said grip being present beneath the lead-sealable cover of the connecting apparatus.