Construction lines (also known as xlines) are temporary linework entities that can be used as references when creating and positioning other objects or linework. For example, you can use construction lines to prepare multiple views of the same item, or create temporary intersections to serve as object snaps.
Construction lines are either circles or straight lines that extend to infinity in both directions. In either case, they do not change the total area of the drawing and have no effect on zooming or viewports. You can move, rotate, copy, or delete construction lines just like other objects.
The regular AutoCAD construction line functionality is still available via the XLINE command. However, the AutoCAD Architecture 2024 toolset construction line feature is designed to give you a more intuitive way of drawing construction lines based on the geometry of existing objects or linework. No command line entry is required.
In most cases, you would probably want to draw construction lines based on segments of existing objects, but you can also draw them by specifying any two points in the drawing area, without regard to existing objects or linework.