Disguised Weapons are becoming more and more of a problem to law enforcement officers and agents, but also to just bar room fights. One, try and be aware of someone ready to use a disguised weapon. They will subconsciously protect the weapon and check the weapon fairly regularly. It is one of the ways we can get a heads up on a possible confrontational situation. Or as a friend of mine would state an aggressive mind set. Someone at a bar with a knife they carry for work, to open boxes with and such, will not deal with it subconsciously the same way a person carrying a sharpened credit card will. It is the mind set of aggression that is key, even a person that is just ready to fight, looking for swing or kick room, will usually show it in some type of aggression mind set, that will move to actual physical changes.
from CTI Consulting https://www.youtube.com/watch?v=P3Y919CX3sE