What bookdealers really mean. A dictionary by Tom Congalton and Dan Gregory (Between the Covers), with additions from other sources
Meaning that a substance has caused a stain that shows through the paper, such as tape that has been used to repair the inside of a jacket, but which has darkened and now shows on the outside of the jacket. What does this tell us? That booksellers and collectors should have their tape dispensers confiscated.