tough, tuff

Tough or tough means strong and durable; not easily cut or broken--
This canvas should be tough enough to make a tent.
This meat is tough; we should marinate it.
Tough, of persons, means strong, hardy, or capable of great endurance, for good or for ill--
The veteran soldiers seem tough next to the new recruits.
He looks like a tough customer.
Tough may also mean hard, or difficult to solve--
This is a tough problem.
Tough luck.

Tuff or tuff  ( rhymes with tough ) means fragments of volcanic rock--
The site of the eruption is covered in tuff, some of it still warm.
People sometimes take a piece of tuff as a souvenir; many of them have mailed them back over the years.

Now that you know that, you can say--
"The bottoms of your shoes are not tough enough to walk across that field of tuff."