A pass is the current inspection being performed on the unit at a specific station. Inspect tracks passes to determine inspection, repair, and tracking times.
For example, Pass 1 is the first time a defect is entered on a unit in a specific area. The second time it returns to the same area, this is known as Pass 2.
After the first pass, Inspect may display a message box prompting the inspector to create a new pass when a unit is entering the area the second time. You can then specify whether it is a new pass or not:
Yes - Add another pass for the unit, will increase the Defects Per Unit (DPU) which will affect quality ratios.
No - Do not add a new pass, just keep the original pass which will not increase the DPU.
Passes are configured when creating or editing a unit at the station itself. This prompt will only display if the station setting “Create Pass” is set to Insert pass if first time, prompt thereafter. For further information on setting up stations., please click the link. 
Tracking point passes are never inserted if you pick a unit from the Unit List. If you use one of the “Goto” buttons, then a pass is inserted.