be as tough as old boots
also be as tough as nails if someone is as tough as old boots, they are very strong and not easily injured 'Do you think Grandad will ever recover?' 'Of course, he's as tough as old boots.'
be as tough as old boots
(British, American & Australian) also be as tough as shoe leather (American) if food is as tough as old boots, it is difficult to cut or to eat That steak I had was as tough as old boots.