When inspecting external functional size on a straight thread (ACME, ISO Metric, UN, etc.), some have a tendency to force the RG-7000 external roll gage onto a part. Keep in mind overly aggressive placement can cause the roll to move or completely slip from the part. Sometimes, this can slam the gage and/or hands on to the part. 
A simple, quick remedy is to place your index finger behind the lower roll as you place it on the part. Slide the roll into place, guide with your thumb for extra support. Now, you can use your hand or fingers to hold the roll in a proper pivoting position.
