"P" rings are used to mount US style keypads, switches, sockets, etc into plasterboard walls
where there is no need for a total enclosure on the rear. They are plastic mouldings that are simple to install, having
'wings' that snap off and act as ratchet clamps on the plasterboard itself.
P-rings are not suitable as alternatives to back boxes in solid walls or where the device fitted requires shielding from
debris in the wall.