The number line is a model that is used to measure, count, order and even operate, which requires a symbolic interpretation. Then, we investigate the conceptions of 72 in service secondary teachers, when they manage the model of the number line associated with order, spatial location and the relative position between numbers and marks. In a workshop carried out through Internet, we found that the participants consider that the usefulness of the model is in the manipulation, and they do not see the need to modify it, despite the requirements of the problem, taking for granted its usefulness and the control that resources could give them, such as the change of the numerical scale. They don't even realize the symbolic properties to interpret the numerability. [For the complete proceedings, see ED630210.]