Dave,
usually you attach brackets to a wall with screws in plastic wall plugs.
For this you would need a hammer drill with masonry bit :-)
You would be lucky to get a firm fix on pebbledash unless the bracket is
wide in comparison to the individual pebbles.
Some choices:
put mastic or other sealant behind the bracket to form a smooth bed
build up over the pebbles with mortar
knock off the pebbles under the bracket and then the bracket sits on the
mortar underneath
screw a piece of treated softwood to the wall to cover the pebbles, then
screw the bracket to the softwood.
HTH
Dave R
"Dave P" wrote in message
...
I placed one of the brackets on the wall and it rocked from side to side
as
the pebble dash is uneven. I am wondering if this will resolve itself once
they are securely attached. The other question is what method of
attachment
should I use?

Thanks,

Dave