From FreeCAD Documentation
- There are several ways to invoke the tool:
- Press the B-spline by knots button.
- Select the Sketcher → Sketcher geometries → Create B-spline by knots option from the menu.
- Use the keyboard shortcut: G then B, then I.
- The cursor changes to a cross with the tool icon.
- Pick several knot points.
- Optionally press M before finishing the input to define the multiplicity of the last defined knot point (this may not always be respected, see limitations for details).
- Optionally press Backspace before finishing the input to delete the last knot point.
- Right-click or press Esc to finish the input.
- The B-spline is created, including a set of internal geometry (weight circles and knot points).
- If the tool runs in continue mode:
- Optionally keep creating B-splines.
- To finish, right-click or press Esc, or start another geometry or constraint creation tool.