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