  The issue of non-local GUT symmetry breaking is addressed in the context of
open string model building. We study ZNxZM' orbifolds with all the GUT-breaking
orbifold elements acting freely, as rotations accompanied by translations in
the internal space.We consider open strings quantized on these backgrounds,
distinguishing whether the translational action is parallel or perpendicular to
the D-branes. GUT breaking is impossible in the purely perpendicular case,
non-local GUT breaking is instead allowed in the purely parallel case. In the
latter, the scale of breaking is set by the compactification moduli, and there
are no fixed points with reduced gauge symmetry, where dangerous explicit
GUT-breaking terms could be located. We investigate the mixed
parallel+perpendicular case in a Z2xZ2' example, having also a simplified field
theory realization.It is a new S1/Z2xZ2' orbifold-GUT model, with bulk gauge
symmetry SU(5)xSU(5) broken locally to the Standard Model gauge group. In spite
of the locality of the GUT symmetry breaking, there is no localized
contribution to the running of the coupling constants, and the unification
scale is completely set by the length of S1.
