A moving plate (12) for protecting tips of male tabs (15) is mounted into a receptacle (18). The moving plate (12) includes a peripheral wall (36) in the form of a rectangular frame, and the peripheral wall (36) includes long sides (43) and short sides (44). Projections (50) are provided on both sides across a center in a longitudinal direction on an outer surface of each long side (43). Recesses (31) shaped to correspond to the respective projections (50) and to be fit to the projections (50) are provided at positions corresponding to the projections (50) on an inner surface of the receptacle (18). Each of the projections (50) has a one-sided dovetail shape projecting toward a central side in the longitudinal direction, but not protruding toward an end side in the longitudinal direction.