The message
from Dave Fawthrop contains these words:

I **HATE** the left hand threads on my
Propane bottles, and after all these years I have to work it out every time
I touch one :-(

I've put an arrow in marker pen on the regulator. Mostly for the benefit
of my son, to be honest, but it's handy.

--
Skipweasel
Pay no attention to that man behind the curtain.