IDIOM ►

learn the ropes, know the ropes

Meaning 1
Ropes are integral (central) to the sport of sailing
Sentence 1
If you want to be a sailor, you need to learn how the ropes work for the jib and main sail.
Meaning 2
to learn how to do anything
Sentence 2
You'll learn the ropes of this job soon enough.

Derivation

Hundreds of ropes were needed to work the sails of the great ships that sailed the oceans in years past. It took many months for a sailor to learn (to use) the ropes. After months at sea, he would have learned the ropes.