triangular mesh          /* use all defaults, including CSTPlaneStress */
boundary = [
   (0,0)
   (20,0)
   (20,10)
   (0,10)
]

hole = [
   (6,3)
   (6,7)
   (8,7)
   (8,3)
]

hole = [
   (12,3)
   (12,7)
   (14,7)
   (14,3)
]

end