The Triple Burner channel relates to the fluid in the upper, middle, and lower body. I believe it correlates to the lymphatic system, since it plays a large part in immunity.
The 5th point is named Wai Guan, or Outer Pass. Think about a pass through a mountainside: It lies between the radius and ulna bones of your forearm, about 2 inches from the wrist. “Outer” refers to the back (posterior, Yang) side of the arm, as opposed to the front (anterior, Yin) surface.
Press TB-5 firmly with a fingertip for 10-20 seconds to stimulate your immune system if you have a cold, flu, or any other type of infection. Allergies can benefit from using this point to regulate an over-active immune system. It’s also helpful for aches on the back of the head and neck.