Change Length 
changes the total length of an unfinished polyline feature. The direction of the edit is determined by a positive or a negative value. This command is available when you draw or edit a polyline feature and right-click a segment.
When you use this command, consider the following:
- A positive value preserves the first vertex and modifies the last segment. A negative value preserves the last vertex and modifies the first segment.
- The angular pitch of z-aware features is preserved. New vertices are assigned interpolated z-values.
To change the length of a polyline feature as you draw it, complete the following steps:
- Add your data and configure settings for editing.
Confirm the feature layer you are editing is editable, the coordinate system assigned to the active map is suitable for the type of edits you're performing, and snapping is configured to help you work efficiently and accurately.
- On the ribbon, click the Edit tab. In the Features group, click Create
. - In the Create Features pane, click a polyline feature template.
To find a feature template containing a specific word or phrase, click the Search box
and enter your search criteria. Search is not case-sensitive. - Click the Line tool
. To override default attribute values or change optional tool settings, click the Active Template button
. - Click the map and create at least two vertices.
- Hover over an unfinished polyline segment until the segment pointer appears.
- Right-click the segment and click Change Length .
The Change Length dialog box appears.
- In the Change Length dialog box, enter the new length and press the Enter key.
To extend the last segment, enter a positive value greater than the current line length. A negative value extends the first segment.
To trim the last segment, enter a positive value less than the current line length. A negative value trims the first segment.
To change the unit format, click the unit drop-down arrow and choose a format.
- Click Finish
or press the F2 key.