appear on dimension arrows
when you select dimensions. The pointer changes to 
when
it is over the arrowhead handles. When you click on arrowhead handle (either
handle if there are two for the dimension), the arrows flip outside or
inside.You can specify placement of arrows with respect to the dimension extension lines: Inside, Outside, Smart, or Document (uses the document defaults, as defined in Dimensions options.
Smart specifies that arrows automatically appear outside of extension lines if the space is too small to accommodate the dimension text and the arrowheads.
Circular arrowhead handles appear on dimension arrows
when you select dimensions. The pointer changes to when
it is over the arrowhead handles. When you click on arrowhead handle (either
handle if there are two for the dimension), the arrows flip outside or
inside.
You can change arrow styles.