A method for assembling an exterior rear view device with a base assembly for attachment to a vehicle, a head assembly with at least one reflective element and/or image acquisition means, with the head assembly being moveable relative to the base assembly, and a retainer assembly, wherein the retainer assembly is adapted to be installed between the base assembly of the exterior rear view device and the vehicle to which the exterior rear view device is mounted, the retainer assembly comprising a retainer means adapted to be mounted on one side to a door attachment portion of a base frame of the base assembly and on the opposite side to a door panel of the vehicle, wherein the retainer means is provided with • at least one opening (322, 351) for allowing at least one datum structural element of the door attachment portion of the base frame to pass thereto, and • at least one guiding projection and/or at least one guiding channel portion for providing at least part of a guiding channel for routing and/or guiding at least one harness (400, 410) from the vehicle to an electric component ( 210, 700, 710) of the rear view device, and/or • at least one sealing portion for covering at least a portion of the at least one harness (400, 410); and a sealing means is adapted to be mounted on the retainer means, the sub-assembly of the base frame, the sealing means and the retainer means forms a channel for positioning a glass run seal, in particular allocated to a cheater panel, the method comprising the following steps: • clamping the retaining means on the door attachment portion of the base frame, • guiding the door attachment portion with the attached retaining means through the opening of the lower case of the head assembly, and • clamping the sealing means onto the door attachment portion and/or the retaining means, with preferably the sealing means and the retaining means being screwed together onto the door attachment portion. the retainer assembly is adapted to be installed between the base assembly of the exterior rear view device and the vehicle to which the exterior rear view device is mounted, the retainer assembly comprising a retainer means adapted to be mounted on one side to a door attachment portion of a base frame of the base assembly and on the opposite side to a door panel of the vehicle, wherein the retainer means is provided with • at least one opening (322, 351) for allowing at least one datum structural element of the door attachment portion of the base frame to pass thereto, and • at least one guiding projection and/or at least one guiding channel portion for providing at least part of a guiding channel for routing and/or guiding at least one harness (400, 410) from the vehicle to an electric component ( 210, 700, 710) of the rear view device, and/or • at least one sealing portion for covering at least a portion of the at least one harness (400, 410); and • at least one opening (322, 351) for allowing at least one datum structural element of the door attachment portion of the base frame to pass thereto, and • at least one guiding projection and/or at least one guiding channel portion for providing at least part of a guiding channel for routing and/or guiding at least one harness (400, 410) from the vehicle to an electric component ( 210, 700, 710) of the rear view device, and/or • at least one sealing portion for covering at least a portion of the at least one harness (400, 410); and a sealing means is adapted to be mounted on the retainer means, the sub-assembly of the base frame, the sealing means and the retainer means forms a channel for positioning a glass run seal, in particular allocated to a cheater panel, the method comprising the following steps: • clamping the retaining means on the door attachment portion of the base frame, • guiding the door attachment portion with the attached retaining means through the opening of the lower case of the head assembly, and • clamping the sealing means onto the door attachment portion and/or the retaining means, with preferably the sealing means and the retaining means being screwed together onto the door attachment portion. • clamping the retaining means on the door attachment portion of the base frame, • guiding the door attachment portion with the attached retaining means through the opening of the lower case of the head assembly, and • clamping the sealing means onto the door attachment portion and/or the retaining means, with preferably the sealing means and the retaining means being screwed together onto the door attachment portion.