I put up one of those floating shelves which took 5 screws. It went on to a
brick / plaster external wall.
The rawlplugs said to use 7mm for the hole but I used a 6mm drill knowing
the drill would probably wander slightly.
3 of the Rawlplugs don't seem to be catching at all and the screws just turn
when they should be getting tight.
I tried upping the screws to size 12 but its just the same. I'm beginning to
think I never went into the brick but into the gaps between the bricks!

I'm not sure if I could get the rawlplugs out without digging into the wall
which I'm reluctant to do as its just been all decorated. Also I can't move
the shelf as its the only wall / height it can be it.

Any ideas on best way to get the screws to take?

Cheers

Steven.