> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/cadd/line-cadd.md).

# Line

A **Line** is a polyline of two or more points used for drafted linework that doesn't need to enclose a region. In bridge drawings you'll reach for it for centerlines, leader lines, breaklines, finish-grade traces, working lines, and any free-form 2D path that traces along but doesn't bound an area. To draw a closed shape that gets filled, use a Rectangle, Circle, or Container instead.

To draw: pick the first point, pick subsequent points, and either double-click or press **Enter** to finish. Right-click during drawing for the in-progress menu (cancel, undo last point, finish). With **Single Segment** mode enabled, drawing ends automatically after the second point — useful for laying out single-segment grid lines and reference lines.

## Geometry

**Name:** Identifier of the line within its parent CAD document. Must be unique within the document.

**Level:** The layer the line is drawn on. The layer controls color, line weight, and dash style. Useful for routing all centerlines to a "Centerlines" layer, all working lines to a "Working" layer, and so on.

**Offset X:** Horizontal offset of the line's origin from the parent CAD document's origin. All vertices are drawn relative to this origin.

**Offset Y:** Vertical offset of the line's origin from the parent CAD document's origin.

**Points (readonly):** The number of vertices currently in the polyline. A valid line has at least two.

**Total Length (readonly):** The end-to-end length of the polyline (sum of segment distances), shown in the project's preferred length unit. Reflects any alignment-driven bending if the parent CAD document is alignment-based.

## Editing

**Add a vertex:** click on the line in edit mode to insert a vertex on the closest segment.

**Move a vertex:** drag the vertex handle to reposition. The two adjacent segments stretch to follow.

**Remove a vertex:** right-click a vertex and choose Remove. The line must keep at least two vertices.

**Offset:** move the cursor to one side of the line and drop to create a parallel offset. For 2-point lines the offset is a true parallel translation; for multi-vertex polylines each segment offsets perpendicularly and corners are intersected.

## Notes

A Line does not close on itself regardless of how many vertices it has, so it can't be filled as a region. If you need a closed path through arbitrary points (e.g., to hatch a non-rectangular footing footprint), use a Container with a closed polyline instead.

When the parent CAD document is driven by an alignment, the line's vertices are bent to follow the alignment — a horizontal line drawn flat becomes an arc over a horizontal curve. This is what produces working lines that follow the bridge geometry without redrawing them on every revision.


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