Which tool is valid for applying resin to a surface?

The resin-fed roller is a specialized tool designed specifically for applying resin to surfaces in composite work. Its construction allows for even distribution of the resin, ensuring that it penetrates the fibers of the composite material effectively while minimizing waste. The roller is typically equipped with a nap that helps to control the amount of resin being applied, preventing runs and ensuring a smooth finish.

Using a resin-fed roller is advantageous because it enables the user to cover large areas quickly and uniformly, which is crucial for achieving the desired strength and structural integrity in composite materials. It is also easier to manage than other tools when dealing with viscous materials like resin, leading to better results in the final product.

In contrast, a pencil, measuring cup, and ruler do not serve the purpose of applying resin to surfaces. While they are useful for other tasks, such as marking, measuring, or mixing, they lack the specialized design and function needed for efficient resin application.