Near Miss with the Weed Whacker Almost Taking Out a Neighbor's Fence

Been in the Chicago area my whole career doing general yard work and handyman gigs, and yesterday was a total heart-stopper. I was trimming around a client's overgrown bed with my trusty Stihl FS 56, focusing on getting that clean edge when the line caught on a buried root and whipped right toward the neighbor's chain-link fence. Missed it by inches, but the fence rattled like crazy and the neighbor came running out yelling about property damage. Had to stop the job, explain it was a near miss, and now I'm double-checking for underground stuff before every trim. Makes you rethink those quick jobs, man. Anyone else had a close call like that on a basic lawn maintenance run?