  This article contributes to the relative BGG-machinery for parabolic
geometries. Starting from a relative tractor bundle, this machinery constructs
a sequence of differential operators that are naturally associated to the
geometry in question. In many situations of interest, it is known that this
sequence provides a resolution of a sheaf that can locally be realized as a
pullback from a local leaf space of a foliation that is naturally available in
this situation. An explicit description of the latter sheaf was only available
under much more restrictive assumptions.
  For any geometry which admits relative tractor bundles, we construct a large
family of such bundles for which we obtain a simple, explicit description of
the resolved sheaves under weak assumptions on the torsion of the geometry. In
particular, we discuss the cases of Legendrean contact structures and of
generalized path geometries, which are among the most important examples for
which the relative BGG machinery is available. In both cases, we show that
essentially all relative tractor bundles are obtained by our construction and
our description of the resolved sheaves applies whenever the BGG sequence is a
resolution.
