Ok I know I'm a nateral blond, but...

My truck has that bit of wood (a piece that runs all the way across behind the base of the seat back) as well, and I puzzled over it for awhile. I don't have an owners manual, but the best I could figure its' purpose seems to be to adjust the base of the seat back for shorter drivers. If you pull the seat back forward and flip the wood forward on the hinges it holds the seat back out a little closer to the pedals.
That would be the seat adjustment , Up seat back ,down seat forward