Synchronize multiple cameras without multicam

[PosadaPhotography]

Hi guys...I have clips from 4 camers, 3 of them run about 2 1/2 hours each and one runs about 55 minutes. For reasons I won't go into, I cannot get all of them to sync using multicam. They don't all start at the same time. They don't have a clapboard that I can sync to. What is the approach I should be taking to sync all four cameras manualy?

[PosadaPhotography]

If I place a marker on each track where I see something I CAN pick, can I automatically sync to that marker?

[PosadaPhotography]

I'm good...found a video...and yeah, I can sync to a marker.