Engineered Tree House construction is not
   something many plans examiners have reviewed
   before. Differential lateral movement
   amongst supports must be provided by
   slider plates, rocker arms, flexible linkages,
   hanging cables and the deflection of connecting
   members themselves. Lateral rigidity
   in the support frame must be provided
   along with simultaneous controlled vertical
   flexibility. Greenwood Engineering has pioneered
   the design and manufacture of special
   high strength live tree fasteners, along
   with related hardware systems.