fixing slate to walls

Quoted text begins.I've also thought about putting several pins into the wall
End of quote.

Hi Norman,

I would cut 10mm deep horizontal kerfs (slots) into the back of the slate
and hang the stone on the angled pins you suggested (8mm stainless steel is
best, brass or copper is OK too). Use some construction-grade silicone to
fill the kerfs.

The kerfs should be cut square in section to allow the pins to get a
positive grip. You could have as many as you think necessary. Four should be
OK.

Fix over-length pins to the studs first, trim them to length (10mm off the
wall), then measure and cut the kerfs using a 4" angle grinder with a
diamond blade. Dry fit the plaque and check for level- dong the pins down
(never UP) with a hammer until the plaque sits true. When it hangs right,
take the plaque off the wall and fill the slots with silicone. Then hang the
plaque as it was before.

Regards,
Simon