In 'Tips and Tricks' are jpg images in imperial and metric format of a 'ruler'. Download the jpg you need and add it to your TFPlan materials. Then follow the instructions on creating a Column with the jpg material 'mapped' to it.
You can now move the column around like a measuring stick (old fashion Transit stick), read the dimension above floor height and Elevate any object accurately by first Selecting the object then right click and selecting Elevate. Just enter the dimension read off the Stick.
It's FREE :-)
Jack