Crossline

Crossline is a term used across several technical domains to describe a line that intersects another feature, or a system of intersecting lines used as a guide. It is not a single formal concept, but a descriptive label found in diverse fields, often referring to lines that aid alignment, measurement, or aiming. In mathematics and geometry, the formal term for a line that crosses another is a transversal; “crossline” appears in technical writing as a more informal synonym.

In optics and aiming devices, crossline refers to the lines forming a reticle in sights and scopes. A crossline reticle consists of intersecting lines that create a central aiming point, enabling alignment and estimation of range or windage. Designs vary from simple crosslines to more complex patterns that incorporate additional markings, such as mils or dots for rangefinding and holdovers.

In surveying, construction, and machine alignment, crosslines appear as grid-like guide lines on instruments, displays, or drawings. They assist with reading coordinates, projecting locations, and ensuring parallelism or symmetry during setup, leveling, and measurement tasks. In graphic design, printing, and CAD work, crosslines function as layout or cropping guides, helping with scaling, alignment, and the precise placement of elements.

Overall, the term “crossline” signals a practical reference framework built from intersecting lines, with the exact meaning tailored to its professional context. See also transversal, reticle, and grid line.