The crush ribs 804 provided to the side surfaces of the head parts 801 of the wire covers 8b, 8c are such that a protrusion height of the crush ribs from the side surfaces of the head parts of the wire covers and a cross-sectional area of each of the crush ribs are established so that the crush ribs are crushed before an excessive force that would damage the head part acts on the entirety of the head parts of the wire covers when the wire covers are inserted into the corresponding wire leading-out holes. Therefore, due to the crushing of the crush ribs 804, the wire covers are press-fitted into the corresponding wire leading-out holes without being damaged.
The wire covers also are inserted into the wire leading-out holes until the received parts 803 of the wire covers butt against the wire-cover-receiving parts 703 provided to inner sides of the corresponding wire leading-out holes and the received parts 803 reach a state of being received by the receiving parts 703.