A first holding member has first stop portions, and a second holding member has one or more support portions and one or more second stop portions. Each of the second stop portions is supported by one of the support portions to be movable in a direction intersecting with a front-rear direction in accordance with resilient deformation of the one of the support portions. When the first holding member and the second holding member are combined with each other, the first stop portions are grouped into a first group and a second group, each of the second stop portions faces one or more of the first stop portions of the first group in the front-rear direction, and each of the first stop portions of the second group faces none of the second stop portions in the front-rear direction.