Final answer:
There is no universally recognized standard height such as 15 m for when a tag line is required for suspended loads; local safety regulations, such as OSHA in the U.S., should be consulted for specific requirements.
Step-by-step explanation:
The question relates to workplace safety when dealing with suspended loads, particularly in construction or industrial settings. Under many safety guidelines, a tag line, which is a rope attached to a load being hoisted, is required to control or prevent unnecessary swinging or spinning of the load. The specific height at which a tag line is required can vary depending on the country and the specific workplace safety regulations in place. However, this question does not provide sufficient context to give a definitive answer as no standard height such as 15 m is universally recognized for requiring a tag line. It's crucial to consult local safety regulations or standards such as those provided by OSHA in the United States, as requirements can differ.