fence / fens/ • n. 1. a barrier, railing, or other upright structure, typically of wood or wire, enclosing an area of ground to mark a boundary, control access, or prevent escape. ∎  a large upright obstacle used in equestrian jumping events.2. inf. a person who deals in stolen goods.• v. 1. [tr.] surround or protect with a fence: our garden was not fully fenced. ∎  (fence something in/off) enclose or separate with a fence for protection or to prevent escape: everything is fenced in to keep out the wolves. ∎  (fence someone/something out) use a barrier to exclude someone or something: Idaho law requires people to fence out cows.2. [tr.] inf. deal in (stolen goods): after stealing the ring, he didn't even know how to fence it.3. [intr.] fight with swords, esp. as a sport. ∎ fig. conduct a discussion or argument in such a way as to avoid the direct mention of something: we were fencing, not talking about the subject we'd come to talk about.PHRASES: side of the fence either of the opposing positions involved in a conflict: whatever side of the fence you are on, the issue is here to stay.sit on the fence avoid making a decision or choice.DERIVATIVES: fenc·er n.

fence side of the fence used to refer to either of the opposing or conflicting positions or interests involved in a particular debate or situation.
sit on the fence avoid making a decision or choice. The two sides of a fence are seen in this and related idioms as representing the two opposing or conflicting positions or interests involved in a particular debate or situation.

see also good fences make good neighbours, the grass is always greener on the other side of the fence, mend one's fences.

fence †defence XIV; art of fencing XVI; enclosing hedge, wall, etc. XVI; receiver of stolen goods XVII. ME. fens, aphetic of defens, DEFENCE.
Hence vb. enclose, screen, protect (lit. and fig.) XV; practise the ‘science’ of ‘defence’ with the sword XVI; (sl.) deal in stolen goods XVII.