Nothing connected to a rail. Just extra jumper/component connections for each wire.
With a 34 pin cable and 2 headers I can map a 16 pin header into different order on the unused holes of the same connector. The jumpers go on the other connector, which is where extra holes per cable wire would be appreciated. To go to Arduino took me a breadboard. A crimp breadboard would fit using cable for a bus is nice is all. I guess I could crimp more connectors instead, breadboards aren't cheap either.