Abstract: A small-sized electronic instrument such as an electronic wrist watch and others in which a plurality of parts are stacked and firmly held together by tightening a screw. The electronic instrument includes a base plate and a screw housing portion, which are integrally molded of a hard plastic material. The screw housing portion includes a bore formed therethrough and adapted to receive a self-tapping screw. When the self-tapping screw is threadingly received in the bore of the screw housing portion, a plurality of parts stacked around the screw housing portion are firmly tightened and held together. The screw housing portion has a shoulder including a step formed therein at the middle portion between the opposite ends. On assembly, the step engages one of the stacked parts. Even if the screw housing portion is pulled upwardly by the tightened self-tapping screw, the part sandwiched between the self-tapping screw and the step limits the upward movement of the screw housing portion on tapping.