Final answer:
Self-piercing rivets are likely used to fasten metal materials, as their design is suitable for tight and resistant attachments in metal objects, often used in the automotive industry.
Step-by-step explanation:
When self-piercing rivets are used as an attachment, it is likely that the material being fastened is Metal. Self-piercing rivets are specifically designed for joining materials without the need for pre-drilled holes. They are commonly used in the automotive industry for attaching metal parts together, due to their strong, tight fit and resistance to corrosion. For example, a metal peg might be used in conjunction with a self-piercing rivet to join it to a metal block, resulting in a secure and durable join.
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