Which piece of equipment is primarily used to check for vertical alignment in masonry?

The mason's level is specifically designed for assessing vertical alignment in masonry work. This tool consists of a straight, flat body with a bubble vial that indicates when a surface is perfectly vertical (or level). When the level is placed against a wall or structure, the bubble will center between the marked lines only when the surface is plumb. This is essential not just for aesthetic purposes but also for structural integrity in masonry construction, ensuring that walls and structures maintain their intended alignment.

While other options like the pointed trowel, story pole, and sled runner have their specific uses in masonry, none are primarily designed for checking vertical alignment. The pointed trowel is used for applying and shaping mortar, the story pole is utilized for marking heights and establishing dimensions, and the sled runner is used in certain masonry applications but does not serve the function of ensuring verticality. Therefore, the mason's level stands out as the essential tool for checking vertical alignment in this context.