ORIGINAL: sticktickler
. . . it has a measuring tool that simply lets you click between two points and drops a line with arrows and the exact measurement of that distance on the line.
In AutoCAD type ''di'' (or dist-either one works) enter, and pick two points. It gives you the absolute distance, plus the delta x, delta y, and delta z values.
For a line with arrows, use dimension, This is more involved in that it requires careful setup to work properly.