A first coupling of a first protector includes a U-shaped inner wall section and a cover. The inner wall section has an inner bottom wall and opposed inner side walls. The cover extends from outer surfaces of the inner bottom wall and opposed inner side walls of the inner wall section to a distal end opening in the first coupling. The cover is open at a distal end. A second coupling of a second protector includes a bottom wall and opposed side walls that are inserted through the distal end opening into a clearance defined between the inner wall section and the cover of the first protector. The first and second couplings of the first and second protectors are connected together so that the second coupling of the second protector is caught between the inner wall and the cover of the first coupling of the first protector.