Those are not nails and are not for slate.
They are fasteners for asbestos tile shingles .
They are used wire part up, and are to prevent wind lift
At bottom edges of shingles.
They are not drivin into the wood., notice , no points.
There is premade holes in the shingles.
To use them on slate would mean making
Holes for every one in two slates
Waste of time and $, as they are not needed at all
On slate.