11
The basic template is a hexagon, having two pairs of equal sides. In 
one pair the sides are opposite and make equal and opposite angles 
with a direction, taken here to be vertical. In the other pair the 
sides are neither opposite or adjacent, and make equal and opposite 
angles with the orthogonal horizontal direction. The six vertices can 
be fixed anywhere within these constraints, and the mid-points of the 
two other non-paired sides are then also fixed. The associated 
distortions allowed within each pair of related segments are  
indicated by the arrowheads, as are their rotational and glide  
reflective relations.
