Tattle-Tape is a security system used in library books. The tape was designed in the 1970s by 3M. It consists of a magnetic metal strip embedded in a strip of thick, clear adhesive tape. This tape is usually affixed deep between the pages of a paperback book, or between the spine and binding for a hardcover book. If a person takes the book and attempts to leave the library premises, an alarm will sound as soon as the book passes through a special gate near the exit. As a result, in order to prevent this from happening, the books require desensitization by the librarian before being given to the library patron to take home. When the book is returned, it is re-sensitized.