A "grounding disk", or "ground disk" connects pins 13-18 together inside a Socapex-compatible connector, allowing the use of 14-conductor, rather than 18-conductor, multi-cable. In this application, wires 13&14 are connected to pins 13-18, rather than 13-18 connecting to pins 13-18 discretely.
ITT Interconnect Solutions: Cannon, VEAM & BIW Connectors
ITT Interconnect Solutions: Cannon, VEAM & BIW Connectors