I wear dress shoes. They are always leather and almost always have leather soles. There is never, to my knowledge, metal in or on them. Yet, sometimes, they set off the metal detector. I don't understand why. and sometimes, the same shoes don't set off the metal detector. For example, in YOW, my home, my shoes never set off the metal detector. At YTB or YSB however, the same shoes which went through the metal detector at YOW with no problem will set the metal detector off.

I'm not a scientist or a cobler so I don't understand these things, but they frustrate me.