('chiefly US') cities in the 'Rust Belt' [=an area formerly known for industry and manufacturing]
When you're riding in a car, you should always 'belt up' [=('US') 'buckle up'] for safety.
That remark was 'below the belt'. = That remark really 'hit' (him) 'below the belt'.
(..) - It's just, you know, there's zombies everywhere. I think the least of my worries is.. - Yeah that's true. ..seat belts. - Yes but no, she's not. she's not. She's only famous when she's Hannah Montana, when she's wearing the wig. -Okay, right. -So.. (..)2009 Zombieland