Two shiftable bus bar unit point sections are simultaneously shifted to allow one of the sections to align with a stationary bus bar unit point section. A coupler slides on the stationary point section toward the just aligned one of the shiftable point sections to couple the same with the stationary point section. The shifting of the shiftable point sections and the sliding of the coupler are controlled by an operating mechanism which employs a cam. A holding device covers sealingly the electrically dangerous exposed end of the other of the shiftable point sections.