12
The basic template is a pentagon, having two pairs of 
equal, non-adjacent sides. In one pair the two sides make 
equal and opposite angles with one direction, the other 
pair with the orthogonal direction; these directions are 
taken here to be horizontal and vertical. The five vertices 
can be fixed anywhere within these constraints, and the 
mid-point of the non-paired is 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.
