You can specify the Reference Level and Origin Level Offset properties for a model group. 
-  In the drawing area, select a model group. 
- On the Properties palette: 
  - Reference Level specifies the level with which the group is associated. 
	 
- Origin Level Offset specifies a height above or below that level. 
	 
 
 
Note: Some group members may not move as a result of entering an offset value. Some elements, such as components, remain on the level line if they are not hosted by another object such as a floor.