10
The basic template is a hexagon, having one pair of equal and 
opposite sides which are parallel. The two sides at either end of each 
of these are equal in length, and within each pair the sides make 
equal and opposite angles with the line joining the ends of the 
parallel sides, taken here to be horizontal. The six vertices are fixed 
within these constraints. The associated distortions allowed within 
each related pair of segments are indicated by the arrowheads, as are 
their translational and glide reflective relations.
0
  
