Using wire wool, ensure that both sides of the joint are clean. With a flux brush, apply flux to both surfaces before heating the area with a propane torch. Starting with the heaviest side, wait for a slight color change to indicate that the metal has reached the required temperature.
Next, apply lead-free solder to the intersection of the two pieces, being mindful that the melted solder will naturally flow toward the heat. When done correctly, the solder will seep out all the way around the joint. Use a damp rag to wipe off any excess.