What is a common use for hacksaws in workshops?

Hacksaws are primarily designed for cutting metal and plastic materials, making this the most suitable option among the choices provided. The blade of a hacksaw features a fine-toothed design, which allows it to make precise cuts through tougher materials such as metals (e.g., steel, aluminum) and certain plastics (e.g., PVC, acrylic). This tool is favored in workshops when tasks require straight cuts or contoured cuts in these specific materials, as the thinner blade is efficient for such work.

The other options mention uses that are more suited for different tools. For example, cutting through thick lumber typically requires a saw with larger teeth, such as a hand saw or a power saw, due to the density and hardness of wood. Shaping metal pipes often involves tools like pipe cutters or files rather than a hacksaw, as those tools are better at creating a smooth finish and precise adjustments. Carving intricate wood designs is most commonly done with chisels, specific carving knives, or similar tools that allow for detailed and controlled cuts in wood.

Therefore, the distinct design and function of a hacksaw for cutting metal and plastic establish it as the correct answer for common workshop use.