What does the term 'course' refer to in masonry?

In masonry, the term 'course' specifically refers to the horizontal layer of blocks, bricks, or stones in a wall. Each course is laid one on top of another, and they are critical in establishing both the strength and the aesthetic appearance of the structure. By ensuring that courses are level and properly aligned, masons can maintain the overall stability and integrity of the wall.

The notion of courses being horizontal is integral to understanding how walls are constructed, as it influences the overall design and function of the masonry work. The term is often used in conjunction with the term "joint," which refers to the vertical spaces between each block or brick in a course.

As for the other choices, while the vertical layout of blocks is important to overall wall construction, it does not define what a course is. Similarly, lateral stability encompasses broader concepts related to the support and anchoring of structures, and the type of mortar used, although important in masonry, is not what defines a course. Thus, the essence of a 'course' is fundamentally tied to the horizontal arrangement of materials in masonry.