The phrase 'On the Fence' is used to describe being undecided about something.
Example of Use: "Has he decided whether he will take the job yet?" Answer: "No, he's still on the fence."
The origin of the idiom 'on the fence' has its roots in Middle English, when the word 'fens', short for 'defens' was originated. Later, an “e” was added to the term to form the word defense as it is used today. Fences often define ownership, and to sit on a physical fence is to straddle a position between two different properties. Metaphorically, sitting on the fence is straddling the position between two ideas without committing to either of them.