{HEAD ~ The buses} of one layer are connected to the appropriate bus of the other layer using through holes located in {TAIL ~ the array} 
{ HEAD ~ The buses } of one layer are connected to the appropriate bus of the other layer using through holes located in { TAIL ~ the array }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL