Each substrate has a first edge and {HEAD ~ a second edge} orthogonal with {TAIL ~ the first edge} 
orthogonal with
Each substrate has a first edge and { HEAD ~ a second edge } orthogonal with { TAIL ~ the first edge }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL