When it comes to armed self-defense, a little knowledge can be a dangerous thing. For example, using a weapon-mounted light is an excellent idea – IF you know what you’re doing AND you’ve practiced under stress. If you don’t, a great many things can go badly wrong. Leaving a gun light on as you sweep a room or house tells the bad guy exactly where to aim his gun and/or mount a physical attack. A far better technique: switch the light on for a quick picture, then turn it off a fraction of a second later and move (while listening for target information). To do that, though, you have to have the right gun light and excellent control of the mechanism. And then there’s whole firing the gun thing . . .