Positioning tool for assisting treatment of a subject in an external radiotherapy programme comprising one or more external radiotherapy treatment sessions comprising: - an inserter having a proximal and distal end which inserter comprises: - an elongated member configured for insertion through an entrance to a canal in connection with bodily tissue of the subject, and provided with an elongated member lumen configured for receiving an effector shaft of a steering guide; and - a guiding strand for guiding the effector shaft into the lumen from outside the entrance to the canal, wherein the guiding strand is disposed at least partially within the lumen and is restrained at or towards a distal end of the guiding strand to limit or prevent sliding of the guiding strand in a proximal direction relative to the lumen, - a removable steering guide having a proximal and distal end comprising: - an effector shaft disposed at the distal end configured for repeatable removable insertion into the elongated member lumen along the guiding strand, and - a handle portion disposed at the proximal end in fixed relation to the effector shaft for controlling the position and/or direction of the effector shaft, wherein the effector shaft comprises a body provided with a guiding strand passage for slidable movement along the guiding strand, the guiding strand passage provided at least partially along a length of the body, wherein the positioning tool is configured to move and/or fix the canal and the bodily tissue of the subject for the external radiotherapy treatment session. - an inserter having a proximal and distal end which inserter comprises: - an elongated member configured for insertion through an entrance to a canal in connection with bodily tissue of the subject, and provided with an elongated member lumen configured for receiving an effector shaft of a steering guide; and - a guiding strand for guiding the effector shaft into the lumen from outside the entrance to the canal, wherein the guiding strand is disposed at least partially within the lumen and is restrained at or towards a distal end of the guiding strand to limit or prevent sliding of the guiding strand in a proximal direction relative to the lumen, - an elongated member configured for insertion through an entrance to a canal in connection with bodily tissue of the subject, and provided with an elongated member lumen configured for receiving an effector shaft of a steering guide; and - a guiding strand for guiding the effector shaft into the lumen from outside the entrance to the canal, wherein the guiding strand is disposed at least partially within the lumen and is restrained at or towards a distal end of the guiding strand to limit or prevent sliding of the guiding strand in a proximal direction relative to the lumen, - a removable steering guide having a proximal and distal end comprising: - an effector shaft disposed at the distal end configured for repeatable removable insertion into the elongated member lumen along the guiding strand, and - a handle portion disposed at the proximal end in fixed relation to the effector shaft for controlling the position and/or direction of the effector shaft, wherein the effector shaft comprises a body provided with a guiding strand passage for slidable movement along the guiding strand, the guiding strand passage provided at least partially along a length of the body, wherein the positioning tool is configured to move and/or fix the canal and the bodily tissue of the subject for the external radiotherapy treatment session. - an effector shaft disposed at the distal end configured for repeatable removable insertion into the elongated member lumen along the guiding strand, and - a handle portion disposed at the proximal end in fixed relation to the effector shaft for controlling the position and/or direction of the effector shaft, wherein the effector shaft comprises a body provided with a guiding strand passage for slidable movement along the guiding strand, the guiding strand passage provided at least partially along a length of the body, wherein the positioning tool is configured to move and/or fix the canal and the bodily tissue of the subject for the external radiotherapy treatment session.