What's the last thing you sat on that wasn't meant for sitting?

problems

I don't know how to describe it.

Air vents for heating/cooling?

Which doesn't sound solid, but these things aren't gonna be damaged unless maybe I start jumping on them

The armrest of a chair. Not the seat cushion of the chair like a normal person would sit in, but the armrest.

Kitchen counter. I just do that sometimes when someone's in the kitchen. I think they find it annoying.

Railroad tracks.

The coffee table.

a bill

The floor