In message , Alan Gould
writes
I read on this group that you should nip the top off your tomato plants
after four trusses have set. Could someone please clarify what this means
please, I'm sure it doesn't mean after four branches off the main stem??

No, it means what it says, after four trusses of tomatoes have set.
Doing that helps the ripening of tomatoes already on the plant. We do
it because by that time, outdoor tomatoes will be cropping, so we are
able to clear out indoor tomato plants to make space for overwinter
crops.
--
I don't miss very much about the years I lived near New York - but oh
my, how the tomatoes ripened there! Hundreds of them on each plant! And
never, ever, a sign of tomato blight. Sigh

--
Klara, Gatwick basin