A method and system for guiding a drill or nail to intersect both bone and an aperture in an implanted implant. In an exemplary embodiment of the invention, a vector is defined interconnecting a path of a tool or cross-implant and the bone and implanted implant. In an exemplary embodiment of the invention, the vector is defined using a light source and two sensors or a light source and a sensor which is on an opposite side of said bone from said source.
