Bus Bar and Battery Feed?

[Rome2009]

Hi. I watched Steve's Build at one sitting. It was extremely interesting. Does anyone know how he went about building the bus bar and how he fed the cables to it from for the positives and negatives of his batteries from underneath the SUV?? I know he had the batteries underneath the SUV and he completely closed off the hole-air tight, but how did he feed the cables back to his bus bar inside the truck? Positive wires had to come thru the truck, but how did he manage to isolate them to get back into the truck? I can imagine the negatives were fairly easy, grounding is not a concern, because it is the point to its cable, but what about the positives?