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The Collation

Using cardboard spacers to fill gaps on the shelf

Sometimes the simplest tools are the best. This post is a tribute to the humble hunk of folded cardboard.1

Cardboard spacer filling the gap on the shelf while two large volumes are in use. All photos are by me, Erin Blake.

You know how when you take a book off the shelf, you stare at the empty space for a fraction of a second, waiting to see if the books on either side stay standing-up? You know the heart-sick feeling of having them start to schlumph before you have time to set the first book down and stick your arm back into the gap? For the past ten years at the Folger, that feeling of helplessness has been replaced by elation because cardboard shelf-spacers exist.2

In closed-stacks libraries, these cardboard wedges also provide a handy spot to hold the call slip. There’s enough friction to keep the paper slip from blowing away, but not so much that you can’t pull it out easily. More importantly for the safety of the books, you don’t have to scootch all the books over to close the gap, then scootch them back again when re-shelving. Even if you’re verrrrrry careful, and move each book one-by-one, lifting instead of sliding, it’s still unnecessary wear-and-tear on the binding of the book (and on the finger joints of the person). It’s also time-consuming.

Call slip and shelf spacer (researcher’s name redacted; it happens to have been a staff member who was showing it to a group of visiting actors, so I could probably have left it in, but I wouldn’t want anyone to think I’m playing fast and loose with the Vault Photography Policy).

Finding a place to store them when they’re not in use can be tricky. It’s easy if there’s growth-space on each shelf, where they can just be left at the ends of the shelves until needed. When the shelves are filled edge-to-edge, though, there are fewer options. This leads to nomenclature. What are these folded cardboard thingies called? When there isn’t one handy, and you hear someone else moving around in the stacks, you shout “Hey, do you see any [fill in the blank] where you are?” An informal survey of Folger colleagues revealed that we have many ways of filling in the blank. In addition to “cardboard thingies” we routinely call them:

  • spacers
  • shelf fillers
  • book Zs
  • accordion doodads
  • book-holder-upper-thingies
  • placeholders
  • cardboard Zs

It’s a bit surprising how many of us use the letter “Z” to describe them: not only is that that the one orientation that definitely won’t work, but being overly pedantic for humorous effect is a feature of library culture. On the other hand, asking someone to please hand you a “book-N” is more likely to get you a book-end than a piece of bent cardboard. Maybe it has something to do with the phrases “S-bend” and “Z-bend” already being common in English, and the pointy corners making it definitely more Z than S? Or maybe it’s because even though they’re used upright, in the N direction, they’re made flat, in the Z direction?

Shelf spacer stored at the end of a row of books, awaiting use.


If you want to make your own book-holder-upper-thingies for home or work, here’s one way to do it:

  1. Determine the depth of the shelf, and the general height of the taller books in that area.
  2. Round those measurements to the nearest whole number (this step is optional, but highly recommended)
  3. Obtain a piece of clean archival corrugated cardboard that’s at least three times as “tall” as the height of the taller books.
  4. With the corrugations running parallel to the long edge, use the measurements from step 2 to cut a strip as wide as the shelf depth, and three times as long as the book height.
  5. Use a ruler and pencil to mark the strip of cardboard into equal thirds.
  6. Using the pencil lines as a guide, fold the cardboard into a Z shape against a straight edge (Tip: if you have access to board shears with a clamp bar, use the clamp as your straight edge. Just be sure not to pinch your fingers. You might also want to tape a note to the handle of the blade saying “No!” to remind yourself that you’re just folding, not cutting).

Which thickness of board you use depends on the size of the books, and what you happen to have on hand. A variety is good. For tall, heavy books, heavy gauge double-walled board is best because it will have more “spring” when folded.  If the books are skinny, though, you’ll want single-gauge board so that you don’t have to fight to squeeze it into a narrow enough “N” to fit the space.

Shelf spacer shown without any weight applied (left) and under the weight of a heavy quarto (right).

The spacers normally get used in the “N” orientation, with the tall sides up against the books to provide maximum support. For some situations, though, it’s handy to use one sideways, so that you see the “N” when you look down at it. That’s what I did when barcoding oversize books in the Folger vault in batches, with each batch filling the top shelf of a book truck. In the photo, all the books to the left of the spacer have barcode flags in them. The spacer shows the gap where they book I’m currently working on came from. After inserting the barcode flag and beeping it into the computer system, I’ll put the book back to the left of the spacer, and take my next book from the right of the spacer.

Shelf spacer temporarily in use on a barcoding truck.

This way, the books themselves never slide across the shelf. Instead, the spacer works its way from one side to the other while serving as a bookmark. The spacer is lying sideways so that I don’t need a third hand to squeeze the spacer when both my existing hands are needed to hold the heavy book.

Each time it’s flexed, the spacer loses a bit of its spring, so eventually it will be too weak to stand up when there’s pressure on it. There’s an easy fix the first few times this happens: fold the folds in the opposite direction, and you’ll regain some spring. When that no longer works, I like to imagine that the spacers go live on a farm, where they spend their final days roaming free, playing with other spacers.

  1. For a formal description of the same tool, see Steven K. Galbraith, Linda Hohneke, and Renate Mesmer, “Book Preservation at the Folger Shakespeare Library (1): The Use of Shelf Spacers,” Journal of Paper Conservation 11, no. 3, (2010): 14-15.
  2. Full disclosure: the feeling of elation is sometimes immediately preceded by a feeling of irritation because it seems there’s never a cardboard shelf-spacer within reach of the book you want, so you have to back-track two or three aisles, grab one, then stomp back to where you were, and by that time you’ve forgotten which of the nearly identical looking brown calf bindings is the one you wanted. This is a small price to pay.