Edit Bar controls: none.
This tool is used to automatically dimension selected entities.
NOTE: This tool can be used in both 2D & 3D drawing layers. The Edit Bar options will differ, depending upon the context.
2D Layer
See Dimension General for standard Edit Bar controls.
Before activating the tool, select all the entities you wish to be considered, using any of the normal entity selection methods. On activating the tool the Automatic Dimensions form appears.
Choose the options you wish to be used:
Overall Dimensions - the extents of the design (draw to the left and below the design).
Main Dimensions - the dimensions (horizontal and vertical only) of the main panels; you can choose where these are drawn.
Linear Dimensions - will dimension any small horizontal and vertical dimensions plus any diagonal lengths.
Angle Dimensions - will dimension any entities not at 0,90,180 or 270 degrees.
Radius Dimensions - will dimension any arcs or circles.
The tool takes any existing dimensions into account and may create a different set of dimensions. The tool does not necessarily dimension every entity; if two entities can share a dimension, then only one dimension is added.
You may get unusual results if you create overall dimensions and then use the tool to add other dimensions. For this reason, it is recommended that either you create all the dimensions in one go, or you create the overall dimensions last.
3D Layer
Before activating the tool, select all the objects you wish to include in the dimensioning.
The overall dimensions for the three axes will be added and the edit bar displayed:-
Settings
From the drop-down list choose the required dimension settings. You can also override these with the edit button 
.
Alignment
You can specify the dimension positions using the alignment options. For each axis choose either Maximum or Minimum. As an example, these two screenshots show the difference between minimum and maximum for the y-axis:-
All three axes set to Minimum
Y-axis changed to Maximum
Dimension toggles
The next three buttons are used to toggle the Width, Height and Depth dimensions on and off.
When you are happy with the dimensions press the Ok button 
.