Aligned Dimension

Aligned dimensions are used when we need to know the distance of a line that is at an angle.  We would use a Linear dimension to create the line by knowing the X and Y distances of the line, but to find out the length of the line itself, we can just use an Aligned dimension.

The tool is used the same way as a Linear dimension.  Choose your first and second points, and drag the dimension text out to wherever you wish to place it.  Note that aligned dimensions will always run parallel to whatever you are dimensioning rather than sticking to an X or Y axis as a Linear dimension would.