Basic Dynamic Symmetry Armature
Main Diagonals: (Blue) from lower left corner to upper right corner (Baroque); from upper left corner down to lower right corner (Sinister)
Reciprocals: (Turquoise ) lines from corners to the top or bottom edge, perpendicular to the main diagonals (at right angles or 90 degrees)
Verticals and Horizontals: (Gray) through the intersections of the main diagonals with their reciprocals
Intersections of the diagonals with their reciprocals: potential focal points (sometimes called 'eyes') since the right angle ensures maximum thrust or movement
This is the construction for a generic rectangle; each aspect ratio gives rise to different points of intersection on the top edge.
See Full Armature Page:
Expanded Dynamic Symmetry Armature