Detailed Drawings > Annotating the Drawing > Dimensioning the Model > Working with Witness Lines > About Witness Lines Associated with Dimensions
  
About Witness Lines Associated with Dimensions
When you create a dimension, the witness lines are created based on the dimension placement location and dimension references. These witness lines do not overlap with the reference geometry. When you move such dimensions, the system automatically clips the associated witness lines so that they do not overlap with the reference geometry. Use the witness_line_offset Detail option to define the spacing between the clipping reference and the start of the witness line.
 
Creo Parametric does not support automatic clipping of witness lines for driving dimensions including driving dimension annotation elements.
You can manually drag witness lines for which automatic clipping is enabled so that they overlap with the reference geometry. In such cases, the clipping references are ignored.