  This article is concerned with a geometric tool given by a pair of projector
operators defined by almost product structures on finite dimensional manifolds,
polarized by a distribution of constant rank and also endowed with some
geometric structures (Riemann,resp.Poisson,resp.symplectic).The work is
motivated by non-holonomic and sub-Riemannian geometry of mechanical systems on
finite dimensional manifolds.Two examples are given.
