When you measure Auto features with the use of a portable arm machine, the thickness type of "None" still applies the thickness value if specified. PC-DMIS applies the thickness to shank style measurements.
When you use a shank probe for measurements, you use the cylindrical shank of the probe to measure instead of the probe tip. To do this, you need to first define sample hits. PC-DMIS can then use the shank to determine the location of the supported feature (Circles, Ellipses, Slots, and Notches).