The double flat symbol alters the pitch of the note to which it is attached as well as any subsequent occurence of the same note (identical line or space) in the same measure.In my personal symphony, this notation means that any tire that I touch on my car will result in a flat for the rest of the day.
On Friday, I drove home without incident and parked in the garage. On Saturday, I woke up to do some errands and got ten feet before I felt it. Walking three-quarters around the car, I found the flat on the driver's side front.
Thinking this was a teaching moment, I called Wynken, my eldest, outside to learn how to change a tire. When we had put the doughnut on, he said, "It looks a little flat." I replied, "No, no, it's just cold out." Backing up another ten feet revealed that he was right.
Flat as a pancake. I tried to manually inflate the doughnut, to no avail. Sidewall split.