A system from which a concealed sanitary fitting can be assembled, the system comprising: a. a connecting member configured to be installed in an installation recess, having a connection interface for fluid connection with a valve function unit and comprising at least two first mounting means (28, 32, 34), b. a valve function unit comprising a counter-connection interface and at least one abutment portion (36, 39), and c. a clamp element (50; 150) comprising i. at least two second mounting means (54; 154) cooperating with the first mounting means (28, 32, 34) and ii. a pressing portion (52; 152), wherein the pressing portion (52; 152) is pressed against the abutment portion (36, 39) of the valve function unit when the clamp element (50; 150) is fixed to the connecting member with the help of the first and second mounting means (28, 32, 34, 54; 154), thereby clamping the valve function unit against the connecting member for fluid connection wherein the connecting member comprises at least two third mounting means (28, 30, 32, 34), and in that the valve function unit comprises at least two fourth mounting means (36, 38, 39) which are configured to cooperate with the third mounting means (28, 30, 32, 34) so as to fix the valve function unit to the connecting member if the clamp element (50; 150) is not used wherein the connection interface and the counter-connection interface define i. a mounting plane in which the valve function unit may be shifted and ii. a central axis transversal to the mounting plane around which the valve function unit may be rotated during an adjustment step in which the valve function unit is in abutment at the connecting member and before the valve function unit is fixedly clamped against the connecting member using the clamp element (50; 150), and wherein the valve function unit cannot be rotated if the third and fourth mounting means (28, 30, 32, 34, 36, 38) are used to fix the valve function unit. a. a connecting member configured to be installed in an installation recess, having a connection interface for fluid connection with a valve function unit and comprising at least two first mounting means (28, 32, 34), b. a valve function unit comprising a counter-connection interface and at least one abutment portion (36, 39), and c. a clamp element (50; 150) comprising i. at least two second mounting means (54; 154) cooperating with the first mounting means (28, 32, 34) and ii. a pressing portion (52; 152), wherein the pressing portion (52; 152) is pressed against the abutment portion (36, 39) of the valve function unit when the clamp element (50; 150) is fixed to the connecting member with the help of the first and second mounting means (28, 32, 34, 54; 154), thereby clamping the valve function unit against the connecting member for fluid connection i. at least two second mounting means (54; 154) cooperating with the first mounting means (28, 32, 34) and ii. a pressing portion (52; 152), wherein the pressing portion (52; 152) is pressed against the abutment portion (36, 39) of the valve function unit when the clamp element (50; 150) is fixed to the connecting member with the help of the first and second mounting means (28, 32, 34, 54; 154), thereby clamping the valve function unit against the connecting member for fluid connection i. a mounting plane in which the valve function unit may be shifted and ii. a central axis transversal to the mounting plane around which the valve function unit may be rotated