PURPOSE: To prevent an electric shock by exposing no blade or blade rest to the connecting faces of connectors, and inhibiting contact between fingers and the blade or blade rest.

CONSTITUTION: A connector 2 has a first insulating wall 12 covering both the top face 14 of a blade 10 projected from a bottom wall 9 forming an end connection 8, and a longitudinally extending edge face 15. A second insulating wall 17, opposite to the exposed surface 16 of the blade 10 and having approximately the same height as the wall 12 while forming a gap between the wall 12 and the exposed surface 16 of the blade into which a fingertip cannot be inserted, is erected adjacent the first insulating wall 16. A connector 3 is also designed to have a blade rest 22 provided inside a slot 21 formed in the end face 20 thereof. The walls 12, 17 are interconnected by three connecting walls 18,19 erected on the bottom wall 9, and the connected walls are integrally fitted into the slot 21 formed in the end face 20 of the connector 3.