Seeing or using a locker in your dream means aspects of yourself which you have kept hidden inside. Consider what items and belongings are in the locker. In particular, to dream of a school locker indicates hidden feelings, knowledge, and attitudes that you need to learn and/or acknowledge.  Dreaming that you cannot open a locker or that your forgot the combination, suggests that you are unsure of where you stand in a particular situation. You feel that you are on shaky ground. If you cannot find your locker, then it also symbolizes  your insecurities about your role or position in a situation.