Which of the following best describes a stringer in stair construction?

The term "stringer" in stair construction refers specifically to the diagonal support that holds the treads and risers of the staircase in place. A stringer is typically a long, sloped board that runs alongside the staircase, providing structural support and defining the angle of the stairs. It acts as a framework for the steps, with notches cut into it to accommodate the treads (the flat parts of each step) and risers (the vertical parts). This structural component is crucial for ensuring the stability and alignment of the staircase, making it an essential aspect of stair design and construction.

In contrast, the other choices describe different components or elements related to stairs. A flat piece of wood for the step pertains to the individual tread, while a vertical support for the railing is associated with the posts or balusters, which hold the handrail. A decorative element of the stair would refer to features like trim or molding that enhance the aesthetic appeal but do not serve a structural function like stringers do. Understanding the role of stringers is vital for anyone involved in stair construction, as they are fundamental to both safety and functionality.