  We present an approach to deriving global properties of accretion disks from
the knowledge of local solutions derived from numerical simulations based on
the shearing box approximation. The approach consists of a two-step procedure.
First a local solution valid for all values of the disk height is constructed
by piecing together an interior solution obtained numerically with an
analytical exterior radiative solution. The matching is obtained by assuming
hydrostatic balance and radiative equilibrium. Although in principle the
procedure can be carried out in general, it simplifies considerably when the
interior solution is fully convective. In these cases, the construction is
analogous to the derivation of the Hayashi tracks for protostars. The second
step consists of piecing together the local solutions at different radii to
obtain a global solution. Here we use the symmetry of the solutions with
respect to the defining dimensionless numbers--in a way similar to the use of
homology relations in stellar structure theory--to obtain the scaling
properties of the various disk quantities with radius.
