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