  All the boundary conditions compatible with the reduction of a five
dimensional spinor field of bulk mass $M$ in a compactified warped space to a
four dimensional brane are derived from the hermiticity conditions of the
relevant operator. The possible presence of metric singularities is taken into
account. Examples of resulting Kaluza-Klein spinor towers are given for a
representative set of values for the basic parameters of the model and of the
parameters describing the allowed boundary conditions, within the hypothesis
that there exists one-mass-scale-only, the Planck mass. In many cases, the
lowest mass in the tower is small and very sensitive to the parameters while
the other masses are much higher and become more regularly spaced. In these
cases, if a basic fermion of the standard model (lepton or quark) happens to be
the lowest mass of a Kaluza-Klein tower, the other masses would be much larger
and weakly dependent on the fermion which defines the tower.
