Terms of art that use prepositions in a nonstandard way

Factual Questions
1

I’m looking for examples of the phenomenon described in the thread title: phrases that have special meaning to a group of specialists, and that begin with a perhaps unexpected preposition. I’m mainly interested in Standard American English, but other Englishes are welcome too.

Examples I’ve thought of:

on study (clinical research). If I become a research participant, I’d expect to be in the study, not on study.

under the statute (law, regulatory). I would probably say according to or in compliance with or following the statute.

Others?

2

People from New York City tend to say “on line” instead of the standard “in line,” but it’s probably all those auto fumes that’s the cause.

3

You sure they aren’t all logged in via their PDAs or something?

4

Under the gun: Wouldn’t it be worse to be in front of the gun?