The Collaborative International Dictionary of English v.0.48:

Fettling \Fet"tling\, n.
   1. (Metal.) A mixture of ore, cinders, etc., used to line the
      hearth of a puddling furnace. [Eng.]

   Note: [It is commonly called fix in the United States.]
         [1913 Webster]

   2. (Pottery) The operation of shaving or smoothing the
      surface of undried clay ware.
      [1913 Webster]