What tool would a mason use to ensure that a line does not move with wind?

The correct choice is the use of a chalk line. A mason utilizes this tool to create straight lines over long distances by snapping a string coated with chalk. By anchoring the line securely and snapping it, a mason can establish a clear reference for laying bricks, blocks, or stones.

In windy conditions, the chalk line remains effective as it can be tightly secured, preventing movement due to gusts of wind. This ensures that the alignment stays true, which is crucial for maintaining the structural integrity and aesthetic appeal of the masonry work. The chalk line's purpose also extends to marking layouts during the building process, making it an invaluable tool for achieving precise results.

The other options, such as a trowel or round jointer, serve different functions related to shaping and applying mortar but do not address the issue of line movement caused by wind. A trig might refer to trigonometry tools or calculations which, while useful in some contexts, do not provide a direct solution for maintaining line stability in windy conditions.