Final answer:
Metal grommets are used for heavy duty applications due to their durability and ability to reinforce holes in industrial-grade materials.
Step-by-step explanation:
For heavy duty applications, metal grommets are typically used. These grommets are made from materials like brass, stainless steel, or aluminum. They are designed to reinforce and protect holes in thick, industrial-grade materials such as tarps, truck covers, or heavy canvas. Metal grommets offer high durability and can withstand frequent use and environmental extremes. It is essential to select the right size and material based on the specific application requirements to ensure the grommet can handle the necessary load and conditions.