Bibliographic Terms: Chain Lines

From John Carter's ABC for Book Collectors:

The widely spaced lines (distinct from the lighter, close-set lines which run at right angles to them) visible in the texture of laid paper, made by the wire mesh at the bottom of the tray in which it is made. They are sometimes imitated in machine-made papers.
If there is any doubt about the genuineness or, in the case of blanks [blank pages - these may be integral to the gathering and called "printer's blanks" or added later as in the case of "binder's blanks"], relevance of a leaf or leaves in a book printed on laid paper, the chain lines, which vary in spacing between different papers, offer a useful preliminary check.