Abstract: An interlocking intramedullary nail system has a nail having an upper extremity, a lower extremity and transverse locking ducts in the upper and lower extremity, a plurality of fixation bone screws adapted to be received by the locking ducts, an attachable lower guide at the lower extremity of the nail, a perforator-guide detachably-fixed to the upper extremity of the nail, and an attachable upper guide at the upper part of the perforator-guide for precisely meeting the locking ducts in the upper extremity of the nail. A method of interlocking an intramedullary nail using this system attaches the perforator-guide to the nail, perforates a bone along its medullary canal with the nail and the perforator-guide until the upper part of the perforator-guide has left the bone, and attaches the upper guide to the upper part of the perforator-guide. Holes are drilled into the bone using the locking ducts of the upper guide and bone screws inserted into the upper extremity locking ducts to secure the nail to the bone.