To correctly obtain mutual attachment positions between a front side component and a rear side component.

The positioning projection 75 of the front side component 25 is inserted into a positioning hole 41 from the front side of a planar structure 4, the attachment part 76 of the front side component 25 is inserted into a relief part 42 from the front side of the planar structure 4, the rear surface of an attachment base board 73 in the front side part 25 contacts a front surface in the circumference of the relief part 42 in the planar structure 4, the front surface 102 of the rear side component 90 contacts the rear surface of the planar structure 4, and a fixing screw 101 is fastened to the attachment part 76 of the front side component 25 by way of a screw insertion hole 98 from the rear side of the rear side component 90. Thus, the planar structure 4 is held in a before and after direction between the front side component 25 and the rear side component 90, then the front side component 25 and the rear side component 90 are attached to the planar structure 4.