A wall-mounting device comprising: - an element to be mounted on or in a vertical building wall, - an assembly receiving device for mounting the element therein and for mounting the assembly receiving device in the building wall, - a positive locking device (19, 20) for mounting the element in the assembly receiving device, said positive locking device (19, 20) comprising a receiving part on the element or on the assembly receiving device, a protruding part on the assembly receiving device or on the element, for engaging in the receiving part, a clamping device (24, 25) for locking the receiving part and protruding part in place against each other, wherein the protruding part is inserted into the receiving part when the element is mounted in the assembly receiving device, and can be pushed into said receiving part in a depth direction until the protruding part reaches an assembled position in the receiving part, wherein the protruding part and receiving part can then be locked in place against each other using the clamping device (24, 25), whereby this locking process stops the protruding part and receiving part being able to move such that they are no longer movable in their locked state, wherein during movement the protruding part runs along a contact surface of the receiving part or the receiving part runs along a contact surface of the protruding part, and on locking in place they are locked in place against each other, and wherein the contact surface (21, 22) is structured in height and the structured in height design enables positive locking with the protruding part or receiving part in various assembled positions, relative to the depth direction, as the protruding part or receiving part moves. - an element to be mounted on or in a vertical building wall, - an assembly receiving device for mounting the element therein and for mounting the assembly receiving device in the building wall, - a positive locking device (19, 20) for mounting the element in the assembly receiving device, said positive locking device (19, 20) comprising a receiving part on the element or on the assembly receiving device, a protruding part on the assembly receiving device or on the element, for engaging in the receiving part, a clamping device (24, 25) for locking the receiving part and protruding part in place against each other, wherein the protruding part is inserted into the receiving part when the element is mounted in the assembly receiving device, and can be pushed into said receiving part in a depth direction until the protruding part reaches an assembled position in the receiving part, wherein the protruding part and receiving part can then be locked in place against each other using the clamping device (24, 25), whereby this locking process stops the protruding part and receiving part being able to move such that they are no longer movable in their locked state, wherein during movement the protruding part runs along a contact surface of the receiving part or the receiving part runs along a contact surface of the protruding part, and on locking in place they are locked in place against each other, and wherein the contact surface (21, 22) is structured in height and the structured in height design enables positive locking with the protruding part or receiving part in various assembled positions, relative to the depth direction, as the protruding part or receiving part moves. a receiving part on the element or on the assembly receiving device, a protruding part on the assembly receiving device or on the element, for engaging in the receiving part, a clamping device (24, 25) for locking the receiving part and protruding part in place against each other,