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Many times user wants to annotate two column bars with a connecting line.
There is a Rake tool button in the Graph toolbar: 
How to
- Click the
on Graphs toolbar to add the annotaton on Graph. - Select the line to adjust the height, lengths on both end.
- Multiple Rake tools can be added to the graph.
- Double click the line to open Object Properties dialog to customize the lines.
- On Dimension tab, user can set Unit to be Scale and enter integers so the line will drop on center of bars.
- Double the * to move the position or double click to edit.