What is indent thing for?

Ok, I've asked around at home and with a few bodies but no one can answer my question. Its probably a stupid question with an obvious answer . What is the indent in the body just above and behind the rear tires :? . On my avatar it is the black part that droops down from the edge of the top of the body. Sorry if my discription isnt very good but I dont know how to explain it.

 

Believe its a holdover from earlier days. (duh) Like the indent on the drivers side of the five just below the drivers seat....where the gas tank filler neck used to be. Can't say what it was for however.

 

ahhhhhhh, that makes sence, I knew it was just something I was overlooking.