He used to have a satellite dish service so he had the main source of video coming from the roof into the attic, then ran coax cables all over the house from there.
I found this 2 video in and 12 video out mega splitter in our attic while tracing some coax cables.
When we first moved in, we had an Optimum cable service then switched to Verizon FIOS a year later. The cable and FIOS lines came in from the side of the house so I had to figure out how to redirect the video outs to various rooms using the existing cables.
This was very time consuming and almost impossible task because there were just way too many coax cables and small 2-way and 3-way splitters all over the house.
I googled for coax cable tester and found this little neat device, which helped me redirect the videos from the existing cables without running any new ones.