Your hands should be free so you can defend yourself, or prepared for an immediate act like unlocking your car. For example: Before you leave the inside of the mall, locate your car keys. Have them ready in hand as you walk through the parking lot to your car. This way you are ready to get in your car immediately, rather than standing around in the parking lot distracted as you rummage through the clutter of your bag. Lock your car immediately after you sit down in it.