As others have said, it is easiest just to take everything out of pockets, and also jewelry, and place it in a pocket of a carry-on. My rollaboard has a small pocket at the top of teh front. I keep it empty just for thi spurpose. Before getting to the security area, I place everything (except for photo ID and boarding pass or e-ticket receipt) into the pocket, and close it up. Then I absolutely refuse to place my bag on the belt until the person in front of me has passed completely through the metal detector and I can move on through and have a line of sight with my bag. This way, even if I am pulled aside and wanded or patted down, I can always watch my belongings.