TR6 mystery flap

["M. Secrest" <msecrest@erols.com>]

This one won't pass the giggle test, but here it is:

        What's the metal flap in the center of the bonnet
        of my new 72 TR6, next to the windscreen, and how does it 
        open?
        
        It's in the place where the fresh air vent is on a
        car I used to own, er, a Spitfire. 

I've looked, but I can't find a reference to it in either of my manuals.

Ponderously,

Martin Secrest
72 TR6
73 GT6

Seen on an auto shop wall:  "I know every nut and bolt on my car
  by its four-letter name."