The advantage of symmetry is that frame bottom parts 1 and frame top parts 2 can be manufactured as two identical modules, but with {HEAD ~ the top module} rotated by {TAIL ~ 180 degrees} or, in other words, placed on its head or inverted 
rotated by
The advantage of symmetry is that frame bottom parts 1 and frame top parts 2 can be manufactured as two identical modules , but with { HEAD ~ the top module } rotated by { TAIL ~ 180 degrees } or , in other words , placed on its head or inverted
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH