This end Y is designed to be used at the end of a 5/16" lateral line in a maple sap tubing system, on the maple tree furthest away from the mainline.
A length of tubing is wrapped around the back of the maple tree and then connected to the outer two branches of the Y. This creates a harness to support the tension of the 5/16" lateral line tubing. Once the tubing is steady, a drop line may be installed to the center of the Y fitting.