That's what a Peaky Blinder was. When someone is hit or headbutted. The show mentions that the band is called Peaky Blinders because of the razor blade on their flat cap. In the program, a gang member can headbutt an opponent and blind or injure him with the razor blade sewn into his cap.
While the Peaky Blinders were a real band, that's not where they got their name from. TEENAGE knife thugs are copying gangsters from the BBC crime drama Peaky Blinders by sewing razors into their caps, it has been claimed. Does anyone really know where that idea came from? I read that real Peaky Blinders didn't actually use razor blades on their caps, and did they prefer to use razors as weapons? Was it just confusion or was it to intimidate your opponents?.