Mobile platforms when negotiating steps and stairs should be able to control theirs posture in order to avoid sudden tilting or falls. In particular, when considering applications for search and rescue operations where users have a very limited time of operation, the motion on stairs should be automated as much as possible. In this way operators can concentrate on their tasks (i.e. search of survivors and/or exploration of dangerous environments) rather than having to focus on the stability of the vehicle. A simple but very effective mechanism called "tail" is introduced. The mechanical design and its control method is presented together with several tests and experiments carried out with a simple tracked vehicle in real environments.