Final answer:
TIG Welding is the correct answer, where a skilled worker manipulates a torch and a filler material manually to join metal parts using heat and solder.
Step-by-step explanation:
The manual method where a skilled worker manipulates a torch and a reel of filler material to join metal pieces is known as TIG Welding. This process stands for Tungsten Inert Gas welding, which is also known as Gas Tungsten Arc Welding (GTAW). The worker holds a torch in one hand to produce the arc and the heat, while feeding the filler metal into the weld pool with the other hand. In contrast, MIG Welding (Metal Inert Gas or Gas Metal Arc Welding - GMAW) typically involves a wire feed mechanism that continuously supplies the filler metal, and Arc Welding commonly refers to SMAW (Shielded Metal Arc Welding) which uses a consumable electrode coated in flux. Friction Stir Welding is a solid-state welding process that uses a non-consumable tool to join materials without melting them.