Which type of fastener is designed for metal-to-metal applications?

The option referring to the type of fastener designed specifically for metal-to-metal applications is a sheet metal screw. Sheet metal screws are designed with sharp threads that can penetrate metal surfaces, allowing them to form a tight connection without the need for pre-drilled holes in thinner materials. They are commonly used in applications where two metal sheets need to be joined together securely.

In contrast, other types of screws, such as wood screws and lag screws, are typically used for fastening wood or heavy materials and are not optimal for metal applications. Wood screws have coarse threads designed for grip in wood, while lag screws have large, heavy-duty threads meant for use with timber and are not suitable for metal joints. Machine screws can be used with metal, but they require a pre-drilled hole and a nut to secure them, making them less convenient for some metal-to-metal applications compared to sheet metal screws, which can be driven directly into the metal.