Annotate a diagram by using callouts
Callouts are annotation shapes that describe other shapes in the diagram, and that can be associated with other shapes. When a callout is associated with a shape, the callout moves with the shape automatically, and if the shape is copied or deleted, the callout is copied or deleted too.
Select the shape you want to associate with the callout.
If no shape is selected, the callout will be added at the middle of the current view, not associated with any shape.
On the Insert tab, in the Diagram Parts group, click Callout.
Click the callout style you want.
Click the callout on the page to type your text.
If you decide you want a different callout style, right-click the callout, point to Callout Style, and then click another style.
Callouts have a yellow control handle at the end of the callout line; the control handle is visible when the callout is selected. Many callout styles have hidden lines by default, but the control handle is still visible when selected. You can make the line visible by right-clicking the callout, pointing to Callout Line, and then clicking a command other than Hidden.
Associate a callout with a shape
If no shape is selected when you add a callout to a diagram, the callout is not associated with any shape.
Click the callout’s yellow control handle, drag it to the shape you want to associate the callout with, and drop the control handle on the shape.
Move the text part of the callout to where you want it in relation to the shape.
Visio also has callout shapes in some stencils. These callouts can be connected to other shapes, but not associated with other shapes – the difference is that callout shapes do not move with the connected shapes, and are not copied or deleted with them.