I am watching a TV program where they are restoring a ruin into a cottage. One thing that left me aghast is the fact that the roof was made with flat, very heavy stone tiles. Ater they rebuild the roof frame with wood, they put the tiles back on the wood by drilling the tiles and using a long nail down through the wood. It's just a matter of time that the nice british weather promotes rust on the nails and a 50 kg tile slides down to kill the poor chap walking by.
I have no knowledge of roof restoration, even less with such unusual tiling, but what is the proper procedure to fasten them without breeding disaster ?