Model-Based Definition > Model-Based Definition > Creating Various Annotation Types > Dimension Properties > Working with Dimensions > About Z-extension Lines
  
About Z-extension Lines
Z-extension lines are lines that Creo Parametric automatically creates when you position a dimension such that the dimension does not intersect its reference in the Z-direction.
Creo Parametric creates a Z-extension line from the end of the witness line and perpendicular to the annotation plane. The Z-extension line extends to the dimension's reference, making the reference easier to locate. If the Z-extension line does not intersect the dimension's reference, Creo Parametric does not create it.
The Z-extension line is attached to the edge of the surface at a distance closest to the dimension witness line. The dimension witness line is aligned with the edge of the surface closest to the point where you place the dimension text in the direction of the witness line. Creo Parametric displays the extension lines as dashed lines in hidden line color.
 
When you create a dimension using the Intersect command on the ATTACH TYPE menu, Creo Parametric creates a Z-extension line only if both the entities are located at the point of the intersection.
When you create a dimension using the Make Line command, Creo Parametric does not display the line and the Z-extension line.
When Creo Parametric creates a Z-extension line, it removes the default gap between the witness line and the dimension's reference.