I can not use the metal detector and remove my belt all the time at Pre (and get yelled at for doing so sometimes). Then through the scanner if I have it on I get an alert and the fingers. It really doesn't matter for me as at 6' 7" my head alerts all the time, yellow box on the head. 50/50 if they ask me to bend over to look at my bald spot and one time they asked to touch my head. I asked them to re-glove before doing so. Belt is off for me.