 Each Physical Agent or Modality has a different use in therapy, depending on the goal of the Physical Therapist (PT) as well as the known benefits and side effects of each tool.In some cases only the Physical Therapist and their Licensed (Under FSBPT in the United States of America) Assistants (Physical Therapy Assistant or PTA) may use these tools.There are some modalities that can be used by the patient/client on themselves with instruction and training such as superficial heating agents or hot packs.