  We discuss a variable flavor number scheme (VFNS) for final state jets which
can account for the effects of arbitrary finite quark masses in inclusive jet
observables. The scheme is a generalization of the VFNS scheme for PDFs applied
to setups with additional dynamical scales and relies on appropriate
renormalization conditions for the matrix elements in the factorization
theorem. We illustrate general properties by means of the example of
deep-inelastic scattering (DIS) in the endpoint region $x\rightarrow 1$ and
event shapes in the dijet limit, in particular the calculations of threshold
corrections, consistency conditions and relations to mass singularities found
in fixed-order massive calculations.
