when i pass traffic control workers on the road, i wave and say thank you. they can't hear me, but most people know what "thank you" looks like when you say it.
plow drivers, road graders, janitors.
these people aren't doing work typically valued and considered important but think what a clustertangle things would be if nobody was there to do that work.
i am also of the opinion that a lot of things would go nicer on the planet if we valued people and the work they do and if we said so.