Today’s expression is cheek by jowl.

Explanation: If you say something or someone is cheek by jowl, you mean that they are very close together,  practically side by side.

Example: Caitlin hated taking the subway at rush hour, she was always stuffed in cheek by jowl with tons of other people.

Origin: This phrase, the first recorded use of which is in 1577, is based on the idea that a cheek and jowl (which can refer to your jaw or chin) are close together,