The other day, I suddenly remembered the ‘clunker’. This was a piece of equipment used by a public library I worked at nearly twenty years ago. It was basically a block used to demagnetise the tattle-tape strips stuck through the spines of library books when loaned, to avoid setting off the alarm when they left the library, and to remagnetise when they were returned. When a book was pushed into the corner of the block, it made a satisfying clunk, hence the name ‘clunker’. This was the only name I knew it by.
The clunker was a rather imprecise security tool. If you became confused about which books were being returned and which books loaned out, you could potentially put demagnetised books back on the shelf, or cause embarrassment by having to recall the patron you just served back to the desk as they set the alarm off with an incorrectly clunked book. You were emphatically told not to use the clunker on cassette tapes and videos, as the magnet would wipe the tapes. I probably did it anyway once or twice on autopilot, but I never heard of anyone complaining that the video they borrowed was mysteriously blank. I also remember working in at least one other library which had a more labour-intensive magnetic block, which instead of clunking, required an unspecified amount of rubbing the front and back of the book on the block as if you were polishing it.
If you have ever bought an ex-library book and you can see a thin metallic strip stuck through the spine, now you know that once upon a time, the book encountered a clunker. I’m sure that some libraries still have this once-innovative system, but radio-frequency identification tags are probably more commonly used.
The clunker! Now I understand. Similar to those used on CDs when people were shoplifting them back in the day.
When I worked in libraries which loaned CDs, it was only the cases on display, the discs were kept in wallets behind the counter. DVDs, however, had those plastic red magnetic strips which could be removed with a special gadget, it didn’t stop some people stealing them though!