To obtain a plastic molding for a top plate or a door material to be assembled with a wood screw without being troubled by the positioning of a fitting screw by enabling a connecting metal of a size large enough to allow the positional shear of a screw hole to be easily fixed to a fitting area on the part side.

This assembly consists of a main body (wainscot part) 2 with angles 5 with one end screwed to the main body 2 and the other end fixed to a wooden member 8 engaged with a top plate 1 with a screw 9 through a fitting screw hole 5p. The wooden member 8 is of such a size large enough to absorb any trouble with a fixture, if the positional shear of the fitting screw hole 5p is generated due to the slight thermal expansion or contraction or deformation of the top plate 1, a door material or the main body 2. In addition, it is possible to dispense with a complicated operation such as the adjustment of a position for fitting a connecting metal. Besides, a nail, a wood screw or a screw of common commercial grade can be used as a fixture and therefore, the ease of operation is significantly enhanced.