I was trimming around a patio area when I hit a rock, and guess where it went?? Yep, right through a one foot by seven foot window! Got real disgusted and moved away from the area to finish trimming and guess what happened next?? Yep, You guessed it, shot another rock right through a three foot by six foot glass door!! Had to shake my head and take a break! I notified the homeowner and told him that I would have someone come out to fix the damage. I told him that I would not accept payment for the lawn service until the damage was repaired and he was fine with it. Just one of those days, after that I called it a day and went home.