12
0
The basic template is a quadrilateral with two pairs of 
equal adjacent sides. In each pair, the sides make equal and 
opposite angles with the same direction of glide reflection, 
taken here to be vertical. The four  vertices are fixed within
these constraints. The associated distortions allowed within 
each pair of related segments are indicated by the arrowheads, 
as are their glide reflective relations.
0

  
