From FreeCAD Documentation
- There are several ways to invoke the command:
- Press the Draft Dimension button.
- Select the Annotation → Dimension option from the menu.
- Use the keyboard shortcut: D then I.
- The Dimension task panel opens. See Options for more information.
- Do one of the following:
- Press E or the Select edge button and select a first straight edge in the 3D view. Repeat this to select a second straight edge.
- Hold down the Alt key, select two straight edges in the 3D view and release the Alt key.
- To position the dimension arc pick a point in the 3D view.
- The displayed angle depends on the edges and the picked point.