[BlueTrain]

I think that some of this applies equally to both concealing a handgun and attempting to decide if someone else is concealing a handgun, too. Your own experience and thought process is at work and because of that, you can easily overlook something by trying to see clues that are not there--because the other person isn't doing what you would do. Hard to explain in just a few words. But if you carry a pistol on your belt or inside the waistband just above your right hand hip pocket, that's where you will expect the other person to have his, when in fact it is in his hand in his left hand front pocket. Or something like that. With experience, though, you get better at it.