The staff is the equipment used to authorize the movement of a train along a specific section of the railway. It consists of metal rods that are carried between stations, indicating the presence of a train on that section of the track. The staff was always accompanied by its holder or support device.

In this system, a train could only be cleared to depart with a staff rod taken from the device if the section of track ahead was confirmed to be free. In this way, operations were carried out with both safety and efficiency.