OK, I have a confession.  Up until my days working at Enterprise Rent-A-Car many moons ago, I didn't realize that there is an arrow on your fuel gauge that points to which side of the car your gas door is.  Up until that time, I always tried to just remember the correct side.  Sometimes I forgot, call me clumsy.  This poor driver not only forgot, but couldn't seem to figure how to park the car properly.