Mystery solved
Found out what "positive/secondary stops" on flashguards are. In the photo below the indentation under the screw hole is a secondary stop. A positive stop (not shown) is a small tab above & left of screw hole and require hand fitting, I've actually installed a few with the tab, it was a pain, just never heard positive/secondary stop. The stops prevent the guard from falling out of position if frizzen screw loosens, always used clear nail polish (cheap loc-tite substitute), learn something everyday.