Bibliography: As it appears in watermark details and on the permalink detail pages, presents identifying information on similar or identical watermarks in other indices.
Chain Line: The marks left by the vertical wire struts of the paper frame.
Date Range: The earliest and latest years in which paper with a particular watermark was used.
Descriptors: These denote discrete elements that make up or contribute to the watermark but which do not determine its overall shape. For example, 'dots' (where the wire mold of the watermark is attached to the frame).
Fabricator: The person responsible for the mill at which the paper was produced.
Family: Groups watermarks which are clearly from different molds but which nevertheless share enough similarities of design that they likely have some relation (e.g., at the level of fabricator).
Laid Line: The marks left by the close horizontal wires of the paper frame.
Mold: The wires onto which wet paper pulp is spread, including the shapes that leave watermarks. Paper mills used multiple molds simultaneously.
Paper Source: The location (including city and mill, if known) where the paper was produced.
Paper Mill: The business that produced paper. Many (generally similar) watermarks can be associated with the same paper mill.
Shelfmark: The library, collection, and codex or collection of loose leaves in which a watermark is found.
Siblings: Groups watermarks which are almost indistinguishable at first glance and which likely have some relation (e.g., at the level of fabricator).
Secondary Width: A smaller measurement of some portion of the interior of the watermark to help better distinguish it from other, similar watermarks.
Type: The broadest category in which a watermark can be sorted. Determined by its overall shape (or the dominant element thereof).
Typesetter: The person responsible for arranging the individual letters of the text as printed on the page, but who is not designated or differentiates themself from the Printer.
Watermark: The negative imprinted shape left in a piece of paper by a wire mold. Since molds were used repeatedly, many pieces of paper can have the same watermark.