Replacing your ball on the Green -Good reminder

When on the green have you ever forgotten to move your ball back after moving it out of your opponent's line?  As you know this is a penalty in both match play and stroke play.  Here is an easy way to remember.  When marking your ball to get out of your opponent's way, turn your marker upside down.  When you go to repalce your ball the upside down marker will be a reminder to move your ball back to its origianl position. Simple but works!