Yesterday both the front and rear interior sidewall on the left hand side of my car had a clean cut, around 3/4 inch long. It was perpendicular to the rim. Both the cuts were identical. I did drive over a rough patch of road and was aware of going over a manhole cover that was raised above the road bed. I assumed that the impact is what caused the damage. I replaced both the tires on the left side, and this morning I was driving and noticed the pressure was down in the new left rear tire. I took it to the tire shop, and they found another identical cut on the interior of the tire. There was no sign of a bubble or impact on any of the three tires. Just a clean cut once again on the inside sidewall, in the exact same spot. It looks almost like someone took a kitchen knife and inserted it. I live in a small rural town and the car was garaged last night. It will be almost impossible for this to be the work of a vandal. So, I am beyond perplexed. I have not had a flat tire in the past decade at least, and to have 3 identical cuts on the same spot on the same side of the car on the inside sidewall with no visible impact damage within 5 miles of driving is incredible. I would be grateful if you have any ideas on what could be causing this. Thanks.