A steering tool includes an internal tube disposed inside an external tube. The internal and external tubes are arranged for longitudinal axial movement relative to one another. A distal end of the internal tube is fixedly joined to a distal end of the external tube. A tube manipulator can cause relative axial movement and distal bending of the internal and external tubes. A locking mechanism can switch between a locked position in which the internal and external tubes are locked at a particular longitudinal axial position relative to one another, and an unlocked position in which there is uninhibited free movement of the internal and external tubes relative to one another. The locking mechanism also includes an intermediate locked position in which there is partially inhibited movement of the internal and external tubes relative to one another.
