batter rule

from The Collaborative International Dictionary of English v.0.48

Batter \Bat"ter\, n.
   A backward slope in the face of a wall or of a bank; receding
   slope.
   [1913 Webster]

   {Batter rule}, an instrument consisting of a rule or frame,
      and a plumb line, by which the batter or slope of a wall
      is regulated in building.
      [1913 Webster]