Lock Plane command
Sets the active plane for the creation of PMI dimensions and annotations. The dimension plane controls how dimension values are calculated and how the dimension and annotation text is displayed.
You also can use the Lock Plane command to change the plane to which a PMI element lies parallel.
When publishing to 3D PDF, it is important to use the PMI tab→Tools group→Lock Plane command 
to set a PMI dimension and annotation plane. Add PMI on the locked plane, and then create the PMI model views you want to publish.
If you set an active plane and then try to place a PMI element that cannot lie parallel to that plane, this message is displayed: The dimension cannot be placed.
In the ordered environment, this means you need to change the active plane using the Lock Plane command.
In the synchronous environment, this means you need to change the active plane, or press F3 to turn the active plane off.
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