Hard as nails
Something people from the south shore of Nova Scotia say when they're referring to something that is tough, they could just use the actual term Tough as Nails but, they don't.
Guy1:HURHURHUR I'M SOO TOUGH HE HE!
Guy2:NO!!! YOU'RE HARD AS NAILS!!! HURHUR
NotStupidGuy: Um, the actual term is tough as nails, guys.
Guy1:NOOOO! YOU'RE WRONG!!
Guy2:NO!!! YOU'RE HARD AS NAILS!!! HURHUR
NotStupidGuy: Um, the actual term is tough as nails, guys.
Guy1:NOOOO! YOU'RE WRONG!!
as hard as nails
someone who is hard as nails seems to have no feelings such as fear or sympathy
John is as hard as nails - I've never even seen him smile.