You posting reminds me of an incident when I was in my twenties. I had bought what was known as a 'Barber Trim Comb' and used it quite regularly. It had a razor blade set in the centre of the comb which allowed for altering the depth of cut. Great for tidying-up my frizzy hair.
Well one evening I gave a 'run' over my hair with a good cutting depth. Using just my right hand, I kept dragging the comb to the same spot on the back of my head. Result, when I held up my shaving mirror to view the back in the bathroom mirror, it looked as if I had been attacked with a Tomahawk.......A bare strip from the crown of my pate down to the nape of my neck.
The following morning I went to the Barber who listened to my story and said to tidy-up the mess he would have to cut my hair very short all over. He did and it was the start of my Crew-Cut period for well over a month.
I lost the comb and could never find it. It's my guess that my wife binned it.
Hans.