Below the hard deck
An age you will not go below when looking for a significant other. Coming in below the hard deck, in naval terms, means having a flight path that will bring you in below the hard deck of the aircraft carrier you're hoping to land on. This will only end poorly.
"Yeah, man, that girl's hot, but definitely below the hard deck. Going to have to pass."
"She's 24."
"I have high standards."
"She's 24."
"I have high standards."