To effectively maintain a cover at a protection position when a first housing is in a separated position.

When the first housing 1a is in the separated position, a force in A direction acts on a protrusion 15p upon application of a force to move a cover 13 from a retreat position to a protection position. On the other hand, a force in B direction acts on the protrusion 15p upon application of a force to move the cover 13 from the protection position to the retreat position. In that case, the protrusion 15p abuts on side walls of a hole 1bx (side walls at width directional ends of an intersection 1bx2) in both the A, B directions, and the movement of the projection 15p is restricted by the side walls.