Mirror Horizontal
Use the Mirror Horizontal option to reflect the object about a vertical line placed in the centre of the object.Instructions
On the Design menu, point to Dimension, and then click Mirror Horizontal.
Select the dimension object.
Figure 1 : Dimension Object prior to mirroring
Once the object has been selected, the dimension object will be mirrored horizontally.
Figure 2 : Dimension Object after mirroring
Once mirrored, you will then be asked whether or not to retain the changes. Upon confirmation, you can select another dimension object.