Modifying a Dimension Element and Dimension Text
The modifications covered here can be performed only on dimension elements; they do not work on dimensions that are placed as primitive elements.
The Change Dimension tool is used to change the symbology of a dimension element to the active settings.
Working with Extension Lines
The points that determine what a dimension element is dimensioning can be thought of as the vertices of the dimension element.
A dimension element must have at least two points or vertices, just as a line must have two end points or vertices. Therefore, you cannot delete one of the extension lines of a dimension with only two extension lines.