grommet holes in replacement panels

[ODIN]

  Some replacement panels such as spitfire boot floor , rear lower inner wing repair panels don't come with grommet holes as per the original.

I know my questions  reveal my sparse knowledge  and  experience and the  answers will probably be very obvious to knowledgeable and the  experienced -please be patient!

What function do the grommets  have?
If it is for drainage then clearly they don't work very well  judging by the rampant rust seen in most folks "before" restoration photographs.
Are they sometimes there, like in the inner sill apertures. to allow spot welder  arms access during original assembly?
So when replacing  such panels,  is the  case  for a  cutting a hole - simply to put a grommet in it?

[daedalusminos]

I believe the main reason for many of those 'grommet holes' was to locate in jigging pegs during assembly on the production line.

[ODIN]

Thanks- that does  makes sense.

I can't see the point of cutting out a hole in a new panel simply to put a grommet in it- there are limits to originality especially under carpets or in the boot...

[heraldcoupe]

The lower halves of the body/chassis assemblies were subject to a dip as part of the paint & finishing process. There were holes at low points to allow drainage as the shells were drawn out of the bath, these account for some of the grommets,

Cheers,
Bill.

[ODIN]

Thanks, that also makes sense