Abstract: A bone drilling device internally drills holes for the implantation of cross-pins in a fractured bone. An intermedullary nail is surgically implanted into a bone, and an adapter rod, a mounting bracket, and a laser guide rod are assembled on the intermedullary nail. Manual rotation of an exposed internally threaded nut in the mounting bracket engages external threads on the laser guide rod, translating the laser guide rod into the intermedullary nail. A flat face of the laser guide rod contacts a flat portion in the mounting bracket to prevent rotation of the laser guide rod during translation. When the laser guide rod is positioned at the desired location, a laser generates a laser beam which travels down the laser guide rod and reflects off of a mirror at a right angle through a drilling hole in the laser guide rod. The laser beam travels through drilling hole in the intermedullary nail and drills through the bone, creating a hole.