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