A mounting part (second member) 12 has a positioning hole 26 to be fitted to an outer peripheral side of a boss 18 disposed on a vehicle interior part (first member) 10, to be positioned thereto. A facing surface 24 of the mounting part 12 is formed into a flat surface. By a slidable-contact of the flat facing surface 24 with a tip end of the boss 18 for a positional alignment, the positioning hole 26 can be fitted readily to the boss 18. A tubular portion 28 is disposed on a surface at a side opposite to the facing surface 24 to be fitted to the boss 18 substantially over its entire length thereof. Such fitting maintains the aligned state, so that a fastening work during fixing of the mounting part 12 by screwing a mounting screw 30 into a cylindrical hole 16 of the boss 18 is facilitated.