If you want to know which connector is C1 or C2 in Revit on Fabrication Parts, you can increase your odds from a 50/50 guess using a couple techniques explained here...
https://www.darrenjyoung.com/2021/11/04/autodesk-fabrication-determining-c1-c2-connectors-in-revit/
Darren J. Young
http://www.darrenjyoung.com/
https://www.linkedin.com/in/darrenjyoung/
