Linear Dimensioning

The Linear dimension is used to create a dimension that is always in line with the X or Y axis.  This dimension will show you the X or Y length of the line you are dimensioning and are needed so you know how much a line changes in either direction.

The image to the right shows what a linear dimension looks like.  Notice how it is parallel to the X-axis, rather then the line that is being dimensioned.

Also to the right, the first point of the dimension is being selected.  To create a linear dimension choose the first and second points of the distance you want to measure.  These points do not have to be anywhere next to each other, and can even be part of two separate lines or objects.

 
Here, the second point is being chosen
 
Once both points are chosen, drag the dimension text out away from the drawing however far you wish to place it