The Collaborative International Dictionary of English v.0.48:

Reglet \Reg"let\ (r?g"l?t), n. [F. r['e]glet, dim. of r[`e]gle a
   rule, L. regula. See Rule.]
   1. (Arch.) A flat, narrow molding, used chiefly to separate
      the parts or members of compartments or panels from one
      another, or doubled, turned, and interlaced so as to form
      knots, frets, or other ornaments. See Illust. (12) of
      Column.
      [1913 Webster]

   2. (Print.) A strip of wood or metal of the height of a
      quadrat, used for regulating the space between pages in a
      chase, and also for spacing out title-pages and other open
      matter. It is graded to different sizes, and designated by
      the name of the type that it matches; as, nonpareil
      reglet, pica reglet, and the like.
      [1913 Webster]