be (as) sturdy as an oak

1. To be extremely durable or hardy in construction; to be able to withstand a lot of stress or rough use. I was apprehensive when he said he was going to build the house himself, but the whole structure is as sturdy as an oak! Don't worry about dropping that end table—it's sturdy as an oak. I was surprised that our tent proved to be as sturdy as an oak during that storm.

2. To have or display extremely robust physical health or strength. Due to a lifetime of physical labor, my father is sturdy as an oak. My grandmother exercises every day and always eats a balanced diet, so even in her 80s, she is as sturdy as an oak. Our father was always as sturdy as an oak, so it took us all by surprise when he was hospitalized by a heart attack at the age of 48.

3. To have or exhibit uncompromising and indomitable resolve, spirit, and strength of character. He was sturdy as an oak in negotiations, so he always got what he wanted. During such times of hardship, this country needs a leader who is as sturdy as an oak. A: "I can't believe that Vanessa is still so positive and upbeat after that horrific accident." B: "I know, she's sturdy as an oak."