Update: switched from a string line to a laser level on this garage job and I get it now
I always figured a laser was a waste of cash for straight runs, until I set one up on a 30 ft garage wall in Gary last week and my corners came out dead on with half the fiddling. String keeps sagging on long runs no matter how tight I pull it. Any of you run a laser outdoors in bright sun, or do you still fall back to string?