I was outside an old industrial park and I noticed a chalk line on the slab outside one of the storefront doors.
It was about an inch back from face of the finish so I suspect it was the line of the studs when they did a refresh of the place. That would make this chalk line maybe two decades old?
I’m certain it survived over the years because this tenant had two doors, and this door was typically locked and unused. But still, that’s a long time for a chalk line to hang around!
Sometimes our most insignificant marks last much longer than we could imagine.