Bob Smith wrote in message ...
In another NG, they suggested panel pins. I would think I would have to
put
a sheet of cardboard between for that, so I don't get a scratched mirror
over time.
For that size glass, 3/4" panel pins. Lay the pin flat on the cardboard,
push down hard and whack it with the edge of a flat sided chisel or similar.
Difficult with a hammer.