to be on the fence

Fence \Fence\ (f[e^]ns), n. [Abbrev. from defence.]
   1. That which fends off attack or danger; a defense; a
      protection; a cover; security; shield.
      [1913 Webster]

            Let us be backed with God and with the seas,
            Which he hath given for fence impregnable. --Shak.
      [1913 Webster]

            A fence betwixt us and the victor's wrath.
                                                  --Addison.
      [1913 Webster]

   2. An inclosure about a field or other space, or about any
      object; especially, an inclosing structure of wood, iron,
      or other material, intended to prevent intrusion from
      without or straying from within.
      [1913 Webster]

            Leaps o'er the fence with ease into the fold.
                                                  --Milton.
      [1913 Webster]

   Note: In England a hedge, ditch, or wall, as well as a
         structure of boards, palings, or rails, is called a
         fence.
         [1913 Webster]

   3. (Locks) A projection on the bolt, which passes through the
      tumbler gates in locking and unlocking.
      [1913 Webster]

   4. Self-defense by the use of the sword; the art and practice
      of fencing and sword play; hence, skill in debate and
      repartee. See {Fencing}.
      [1913 Webster]

            Enjoy your dear wit, and gay rhetoric,
            That hath so well been taught her dazzing fence.
                                                  --Milton.
      [1913 Webster]

            Of dauntless courage and consummate skill in fence.
                                                  --Macaulay.
      [1913 Webster]

   5. A receiver of stolen goods, or a place where they are
      received. [Slang] --Mayhew.
      [1913 Webster]

   {Fence month} (Forest Law), the month in which female deer
      are fawning, when hunting is prohibited. --Bullokar.

   {Fence roof}, a covering for defense. "They fitted their
      shields close to one another in manner of a fence roof."
      --Holland.

   {Fence time}, the breeding time of fish or game, when they
      should not be killed.

   {Rail fence}, a fence made of rails, sometimes supported by
      posts.

   {Ring fence}, a fence which encircles a large area, or a
      whole estate, within one inclosure.

   {Worm fence}, a zigzag fence composed of rails crossing one
      another at their ends; -- called also {snake fence}, or
      {Virginia rail fence}.

   {To be on the fence}, to be undecided or uncommitted in
      respect to two opposing parties or policies. [Colloq.]
      [1913 Webster]