Fixings for wooden panel - what are they?

[Dezzy]

It's MDF and i can't think of any other reason than it's cheap and easy to cut, although when they get wet don't they swell? The screws go into plastic and therefore will probably have been Flange Head Pozi Drive Self Tapping Screws (i don't have any either) and i'd expect then to have been black. Not sure about size.

I was thinking along the same as Adrian, Marine Ply and using the compressed cardboard one as a template.