2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55246A general rule determining how extremal branes can intersect in a configuration with zero binding energy is presented. It is derived in a model independent way and without explicit use of supersymmetry, solving a set of classical equations of motion. When specializing to M and type II theories, it is shown that some intersection rules can be consistently interpreted as boundary rules for open branes ending on other branes.12 pages, Latex, uses crckapb.sty. To appear in the proceedings of the Cargese '97 summer schoolHigh Energy Physics - Theorytext