I know about the plates that one installs onto a stud where wiring
passes through it, but that is possible only on the side that is not yet
finished. What about the other side, the already-finished side? My
brother-in-law says that in Canada they use metal sleeves through the
studs, and the wiring then goes through the sleeve and is protected from
both sides. When I've asked here in the US, people say it sounds like a
great idea but they've never seen such a thing.

Are these available, and if so where?

--
MB

Whether you vote Democrat or Republican in November, the country will
still be run from boardrooms in the USA and elsewhere, not by your
elected representatives.