It was one of those things a buddy of mine who used to work in corrections taught me. I'm going to school to eventually go into federal law enforcement and it was something he figured might come in handy one day for me to know. He said he used to carry it in case he got locked up with his own cuffs and his clothing was taken (as an attempt to escape). It is flat so it can be hid anywhere. It can also be used as a scraper for a flint, as it is made from a hacksaw blade (which is why I mention it).