('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'.
(..) But when you're naked, it's like... It's so final. You're just, "Well... ...that's it. There's nothing else I can do." That's why I like to wear a belt when I'm naked. Because I feel it gives me something. Some, you know, "I'm naked, but, you know..." I'd like to get pockets to hang off of the belt. That would be... Wouldn't that be the ultimate thing? To be naked and still be able to do this. I think that would really help a lot. A mental institution? (..)1991 TvShow: Seinfeld Title: The Truth Season: 3 Episode 2