This is the highest level of support in a three-tiered technical support model responsible for handling the most difficult or advanced problems. It is synonymous with level 3 support, back-end support, support line 3, high-end support, and various other headings denoting expert level troubleshooting and analysis methods. These individuals are experts in their fields and are responsible for not only assisting both Tier I and Tier II personnel, but with the research and development of solutions to new or unknown issues. Note that Tier III technicians have the same responsibility as Tier II technicians in reviewing the work order and assessing the time already spent with the customer so that the work is prioritized and time management is sufficiently utilized.