somebody wrote:
In message , Andrew Gabriel
writes

or protruding wires. When I skim, I cut a tight fitting cardboard
square or rectangle and push it into the front of the box. This
helps keep the plaster and PVA out of the box. I've never seen
a plasterer to this though. Finding the box afterwards can be
difficult if you don't know exactly where it is and it's been
skimmed right across. Remove the cardboard before the plaster
sets completely.

Huh? I've had a number of rooms skimmed now, no cardboard and no
difficulty finding the back boxes... I really can't see how on earth
they'd get 'lost'?

Never tried the cardboard trick myself, or used the purpose-made plastic
items that I thik Screwfix et al sell for this purpose; however I've
certainly experienced the problem of "WTF was that light switch" after
having walls plastered by a pro.

David