Know the Ropes

A straightforward piece of nautical training turned idiom. Sailing ships were controlled by an enormous, complicated web of rigging, and one of the very first things a new sailor had to master was which rope did what, and how to tie, splice, and handle each one correctly. A crew member who genuinely understood the rigging "knew the ropes"; one who didn't was a liability. The phrase appears in a literal, nautical sense in Richard Henry Dana's sailing memoir Two Years Before the Mast (1840), and had already shifted into general, non-nautical figurative use by the late 19th century, describing anyone who'd learned the practical details of a job.