Under Dash Shelf securing screws

[chrisjp]

Can anyone tell me what sort of screws - threaded or self tapping - are used to secure the under dash shelf to each side of the car?
My shelf has been off for a while and I can't find the screws that I removed. I can't see by looking (even with the trim panels off) whether the side body panels have captive nuts into which screws are threaded, or whether they are simple self-tappers.