Offset

		The Offset tool can be found on  the Modify toolbar and is used to create a line or other object parallel to an existing one. Start the command by clicking on the icon.  You will then be asked for the Offset distance.  This is the distance between the original line and the Offset line that will be created. Next select the item you wish to Offset.  Once that is done, AutoCAD will ask for the side you want to Offset to.  To set this, click to whichever side you want the new Offset line to be created on. In the example to the right, the left line was the original, so I clicked to its right in order to create the Offset line on the right side of the original.
		The inner arc in this image was created without knowing the center point or diameter or any of the end points of the arc.  The outside arc was first created, and then the second arc was made using an offset.  Multiple items can be offset in one command.  Once the Offset distance is set, you can select as many parts of your drawing as you want to Offset before the command ends.  You will only be able to do one object at a time though since you have to select the side you want to Offset to each time.