Originally Posted by samuelsmith
Aren't they floor board plugs? Incase you get water in the floor board and need a quick drain. Jeeps have them also.
This could be it....or, they may be used during assembly on the assembly line to access some part underneath.
Pop one out and see if there's a nut, a bolt, or some other fastner right below it.
On the 2011's and up models, the rear seats are removed to gain access to a cover to get at the fuel pump(s) without having to drop the gas tank.