hard as nails

bite one's nails

To worry or fret over something.

bone hard

As hard as a bone, rock hard.

cold hard cash

Money, regarded as an incentive that can override any doubts or ethical concerns.

die hard

Of a living being, to die only after a desperate struggle for life.

drive a hard bargain

To negotiate forcefully.

give someone a hard time

To cause difficulty or make trouble for someone.

go hard with someone

To lead to someone suffering; to place someone in difficulty or danger.

hard at work

Labouring with great effort and diligence; working hard.