Final answer:
Manual welding machines are used to join metal materials using heat and solder. Welders wear protective gear to shield themselves from the electric arc and thermal energy.
Step-by-step explanation:
Manual welding machines are used in the process of joining metal materials using solder and heat. Different sources of fuel such as gas, electricity, and laser can be used for welding. The process involves melting the metal pieces together using a welding rod or wire. The welder wears protective gloves and a helmet to shield themselves from the electric arc and thermal energy produced during welding.