There used to be some kind of thinning thing for men's short hair that I found around the house when I was young. It looked like a cross between those old "Daisy" razors and a regular men's hair shaver. I ran it through the back of my all one length hair and it basically shredded the cuticle and left it thinner in some spots and untouched in others.
I don't know what to compare it to: perhaps a badly cut lawn?
Dogs and nature abhor a vacuum.