^^^^ This, have to agree with kids about - and as they say, "Safe as houses".
Also, what happens when the mirror has to come down when decorating or moving.
When I had the en-suite re-tiled I had to take a mirror off the wall, approx 3x3ft and was screwed at 4 corners and glued to old tiles.
Was not an easy job getting it off - had to break it which was quite dangerous with all the splinters of glass and a real mess!
So its a "No Glue" for me!
