  It is shown that even a weak out-of-plane attraction, V -> 0, can form
real-space pairs in the body-centered tetragonal lattice despite the presence
of a Hubbard repulsion and a fully developed three-dimensional kinetic energy.
In the hole channel, the pairs have d orbital symmetry which, following
Bolgoliubov's argument, translates into a d-symmetric macroscopic
superconducting order parameter. The findings help to understand key features
of La_{2-x}Sr_xCuO_4 and further support the real-space mechanism of
superconductivity in cuprates. The rules of real-space superconductivity are
formulated at the end.
