Where do gridlines normally intersect on a blueprint?

Gridlines on a blueprint are an essential component used by architects and engineers to provide a framework for locating various structural elements within a building plan. They serve as reference points that facilitate the accurate placement of components like walls, columns, and other structural features.

The correct answer highlights that gridlines typically intersect at the centerline of columns. This is because columns are critical structural elements that provide support to the building. By positioning the gridlines at the center of these columns, the blueprint enables clear communication regarding the precise placement of the columns relative to other design elements in the structure. It ensures accurate measurements and alignment throughout the construction process, which is vital for both structural integrity and aesthetics.

Other options refer to different potential points of interest in a building, but they do not align with the standard practice regarding gridline intersections. While entry points of ducts, corners of the building, or midpoints of walls may be significant for other reasons, they are not where gridlines converge based on standard architectural convention. This distinction helps maintain clarity in the design and allows for effective coordination among different trades involved in the construction project.