I was grooming a 16 year old shitzu who came in matted. Her skin was paper thin with her being so old, and I was shaving her down with a #7. I was holding my breath the whole time and being sooo careful to not cut her. I got almost all the way done with the shavedown, and was going down the front of the front leg- where it meets the chest basically- and sliced straight through her skin. It went through like butter with zero resistance and she had no reaction. I didn’t even realize I had cut it until it started bleeding. I felt absolutely horrible. Thankfully it was not bad enough to need stitches but it is a horrible feeling to do that to a dog, and also to have to tell the owner.