The Distance Tool add-in allows you to measure distances on graphs and plots you've made in JMP. The tool is very easy to use as it uses a drag and drop control scheme to perform measurements. The figure below shows the tool's main command window and the various options available to you.
In addition to measuring distances, the tool also allows you to trace out a path or polygon shape and measure the enclosed area. The image below highlights some of the advanced features that the tool offers.