The DB15, also known as a DA15 or Gameport connector, has been around almost as long as personal computers. If you're like most people, you probably used it for joysticks and game controllers through the 80s and 90s. Maybe even for MIDI instruments. Today it's mostly seen on legacy setups, or purely as a data port.
This female/female or male/male coupler attaches directly to any plate or bulkhead with the appropriate cutout, and acts as a passthrough.