How do I get rough palms?

Question

Any specific ideas? (don't suggest "become a mechanic", for example. Ideally, name an activity). THanks.

Answer 1

rock climbing.

Answer 2

pull tug-of-war.

Answer 3

my classmate plays guitar and his palms are really hard. but he told me he got them from playing for around 8 hours everyday for a month.  

Answer 4

Hard work.