How to Make Non-Adjacent Lines Parallel in FreeCAD

Applying a parallel constraint to non-adjacent lines in FreeCAD allows you to align the direction of separated edges within the Sketcher workbench without creating physical connections between them. This guide provides a direct, step-by-step process for selecting separated line segments, applying the constraint using toolbar icons or keyboard shortcuts, and troubleshooting common over-constraint errors that may occur during the operation.

Step-by-Step Guide

  1. Enter Sketch Edit Mode: Open your document, navigate to the Sketcher workbench, and double-click the sketch containing your target geometry in the tree view.
  2. Select the First Line: Click directly on the body of the first line segment so that it changes color (typically to green), indicating it is selected. Do not select the endpoints.
  3. Select the Second Line: Hold down the Ctrl key (or Cmd on macOS) and click on the body of the second, non-adjacent line segment. Both lines should now be highlighted.
  4. Apply the Parallel Constraint:
    • Click the Constrain parallel icon on the Sketcher constraints toolbar (represented by two parallel diagonal lines).
    • Alternatively, press the default keyboard shortcut P.

Once applied, FreeCAD adds a numeric parallel constraint marker to both segments, ensuring their slopes remain equal regardless of distance or position.

Important Considerations and Troubleshooting

  • Select Edges, Not Endpoints: Ensure you click the line segments themselves rather than their vertices. Selecting vertices instead of edges will prevent the parallel tool from functioning properly.
  • Over-Constrained Sketches: If your sketch turns orange or red after applying the constraint, the lines are already locked by conflicting dimensions or constraints (such as both lines having individual horizontal/vertical constraints, or fixed angle dimensions). Remove any redundant orientation constraints to resolve the conflict.
  • Construction Geometry: The parallel constraint works identically on regular geometry lines and construction (blue) lines. You can make an active feature line parallel to a non-adjacent construction reference line using the same procedure.