Binding beam

from The Collaborative International Dictionary of English v.0.48

Binding \Bind"ing\, a.
   That binds; obligatory.
   [1913 Webster]

   {Binding beam} (Arch.), the main timber in double flooring.
      

   {Binding joist} (Arch.), the secondary timber in
      double-framed flooring.
      [1913 Webster]

   Syn: Obligatory; restraining; restrictive; stringent;
        astringent; costive; styptic.
        [1913 Webster]