If the hot shoe (flash mounting point) on your Canon Digital Rebel camera is loose, then your flash might not be stable on the camera or operate properly. It may not be immediately obvious how to fix it. This video shows you how to do it with a couple of flat screwdriver tips and a tiny PH000 Phillips head screwdriver. (They often sell these in sets of five or seven.) The trick is to lift up on the clip so that the front lip clears its catch and it can slide back. You may need to lift it over the screws as well if they’re really lose.
(Yes, that’s a Spider Man bandage. I have an excuse; I’m a daddy.)