Bags that you check cannot be locked anymore. Process now is you check in and bags must be unlocked. Once you get tickets you then give bags to security personnel who send them through scanner and open them for inspection if they desire. You cannot touch bags at anytime after you have handed them over to security personnel. (Note system may not be up and running at all airports yet.)
Carry-on bags must be unlocked when you go through security into the gate area. You can of course lock it after you passed through security, but then they are subject to random search ar time of boarding the plane. Also, if you can, wear sneakers. Many are requiring people to take of any other shoes (even sandals) when going through security.