It compares the the nail to how hard it is.
Cora is described as "hard as nails."
This is a simile comparing someone or something to nails. Nails are hard and tough, so this person or thing is being declared to be very hard and tough.
its a simile like Small as an ant a simile is a phrase with like or as
As hard as nails (usually about a person) As hard as diamond As hard as rock
A common simile for "as hard as" is "as hard as a rock." This comparison emphasizes extreme toughness or difficulty, suggesting that something is unyielding or challenging. Other examples include "as hard as nails" or "as hard as steel," which similarly convey strength and resilience.
Think about this and you can figure it out. Are nails hard and tough? The kind made of steel certainly are - this simile compares someone's strength and toughness to that of a nail.
It is simile because it have as or ilke
As hard as a brick
One simile I have for you is, ''The rock was as big as an elephant ''.
Billy boy was tough as nails.
it makes your nails grow but it doesn't make it hard
The turtles shell was hard as diamonds.