She wore a skirt that reached 'below' her knees. = The bottom of her skirt was 'below' her knees.
The temperature ranged from 5 'below' to 10 above. [=from −5 degrees to 10 degrees Fahrenheit]
That remark was 'below the belt'. = That remark really 'hit' (him) 'below the belt'.
(..) Anything goes. It's Thunderdome. -Is someone helping you? -Stay back. Where is it now? There's overlap between the needle and slash below the E. How low are you gonna go? Oh, I've been in the slash many times. This is nothing. You'll get used to it. Just put it out of your mind. Have you ever been completely below the slash? Well, I almost did once and I blacked out. When I came to the car was in a ditch and the tank was full. I don't know who did it. (..)1998 TvShow: Seinfeld Title: The Dealership Season: 9 Episode 11