not a teacher
The phrase "not enough room to swing a cat", means the space/room is small and usually awkwardly so.
It's often thought to refer to the "cat o' nine tails", slang for a type of whip once used in the navy. However there is some doubt about this origin.
No room to swing a cat
"Hands folded on his desk" is simply descriptive, it's not an idiom.
A photo of hands folded on a desk.