A sheet metal covering used for protection is called______.

The correct answer to the question regarding a sheet metal covering used for protection is sheathing. Sheathing serves as a protective layer on the outside of a structure, often providing a barrier against moisture and environmental elements while also offering structural support. It can be made from various materials including metal, which helps in shielding underlying materials from damage.

In contrast, insulation refers to materials designed primarily to reduce heat transfer, while refractory pertains to substances that can withstand high temperatures and are usually used in furnace linings. Coating generally involves a painted or sprayed-on application designed to protect surfaces, but it does not refer specifically to a structural sheet metal covering like sheathing does. Understanding these definitions clarifies why sheathing is the appropriate term for this type of protective layer.