Callout Dimension
The Callout Dimension 
tool adds a
leader line pointing from a location on the drawing to a note placed nearby.
Creating a callout dimension
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Select the Callout Dimension tool.
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Pick the callout reference point — the feature the callout points to.
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Pick the callout location — where the note text is placed.
The Text and Tolerance input boxes let you set the callout text and add a tolerance. See the section overview for the options shared by all dimension tools.