I never heard of 'reglet' before either:
Reglet
(n.) 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.
(n.) 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.

And what is a 'chase' in book making?