An assembly, configured to be mounted on a structure, includes a duct in the form of a hollow tubular body of which an inner space defines a zone for receiving a wiring harness. The duct is flexible and includes a longitudinal slot. The assembly includes attachment lugs rigidly connected to the duct and configured to be assembled to the structure. The assembly includes, at longitudinal edges of the duct, on either side of the slot, a pair of recesses with one recess per longitudinal edge. The receiving zone is compartmentalized into two longitudinal channels by a longitudinal separator extending from a longitudinal base of the duct to the slot. The separator has a recess in the same cross-section as the pair of recesses of the duct. The assembly includes a clamping member configured to be inserted into the pair of recesses of the duct and the recess of the separator.