The message
from "Dave Plowman (News)" contains these words:


Some boxes also have only one adjustable lug - which most would fit so it
can be used for horizontal fixing.

And many boxes have -- or at least in the past had -- no adjustable lugs :-(


See also my point about the large
plastic lugs at the top fouling some dimmers, etc.

Been there, done that, got the t-shirt. Often :-(


Whilst they may still be current catalogue items, I think we're dealing
with something which is largely a relic of the past. I dare say I could
probably find one or two in a box of old bits somewhere around my
storeroom, but then I could also find a few packets of mounting flanges.
Remember them? Used to use them on 4 lug single-gang metal back boxes.
Fix flange to box using two of the lugs, then fix box to skirting by
woodscrews through the face of the flange. A whole lot simpler ( and
easier to align) than screwing through the side of the box into the
thickness of the skirting. But then flange boxes became readily
available and the problem was solved in a different and simpler way.