Abstract: A system of keying and fastening together a pair of mating connectors is provided where each of the connectors is of the type having forward and rearward thin walled metal shells clinched together about their flanged edges to retain a housing means therewithin, with the forward and rearward shells having adjacent aperture lateral flanges. The system includes a pair of key members each securable to the front of the forward shell at a respective lateral flange, seated within correspondingly hexagonally shaped flange apertures of the forward shell only, held against the front surface of the rearward shell. On one of the connectors a pair of jackscrews extend through the flange apertures and through with the apertures being slightly larger than the jackscrew portions extending therethrough, the jackscrews being apertures of the key members of the one connector, secured rearwardly of the connector by means permitting rotation after mounting and simultaneously securing the key members to the connector.