Sheetmetal > Designing in Sheetmetal Design > Using Notches and Punches > About Skipped References
  
About Skipped References
Skipped references are notch or punch placement references that have not been defined. Skipped references can be either intentional, if you are unsure of a notch or punch placement reference, or unintentional. In either situation, you must define a skipped reference to place a notch or punch correctly.
Skipped references are reported with the status comment References are missing.