When a part of something is used to represent the whole
"Friends, Romans, Countrymen, lend me your ears" (Julius Caesar).
"Stop moving so slow, I've got mouths to feed" (Ludacris).
"All hands on deck!" (Peter Pan)
"One hand feel on my steering wheel, the other on my heart" (Taylor Swift).
"Come and rest your bones with me" (Maroon 5).