Which tool is appropriate for marking 360 degrees around the outside of tubing?

The correct tool for marking 360 degrees around the outside of tubing is the ferrule. A ferrule is a cylindrical metal tool that is designed to make a precise mark or line around the tubing's whole circumference. When the ferrule is placed around the tube and rotated, it provides a clear reference line, ensuring that the marking is uniform and accurately positioned for tasks such as cutting or welding. This precision is essential in instrumentation and piping work, as accurate measurements and markings are crucial for the integrity and functionality of installed components.

In contrast, other options such as a laser level are typically used for aligning and leveling over distances rather than marking around tubing. A rubber band and string may not provide the rigidity and accuracy needed; they could easily shift or stretch, leading to imprecise markings. Thus, the ferrule's design specifically caters to the requirement of achieving a consistent 360-degree mark around tubing with confidence in the result.