One staple of childhood quickly became those marble notebooks. They have that signature black-and-white cover and faint lines. Blue running horizontally for writing, and red for…what? Why do notebooks even have those margins in the first place?
The reason is actually rather surprising. One initial explanation might point to giving teachers a place to write comments. But that was not their original intention. This signature design is actually thanks to a source typically viewed unpleasantly: rodents.
Rodents loved a midnight snack of notebook paper; margins kept everyone happy
When writing important information, left to right, every piece of information could be important. So, writers made use of all they could in a notebook. Yes, the inner spine could make writing difficult. But at least any words written there would be safe.
Safe from what? Hungry rats, mice, and the like. Any papers lying around could become snacks for these rodents, and naturally, they started on the loose edges where they could easily bite and tear off some paper. Their feast would take important notes with them. To resolve this, notebooks came to include red margin lines. These marked where a person should stop writing in case their notes became a snack.
Margins are red, other lines are blue, all this is meant to help me and you
Why are the those margin lines in red? And why are the writing guidelines blue? Answers vary a bit by source. John J. Pleger’s book Bookbinding and Its Auxillary Branches claims this makes notebooks more readily made. Color theory further explains that the red line will draw necessary attention to where writers should stop while the blue lines are faint, visible enough to guide but not invasive enough to affect reading.
Further theories suggest that blue lines don’t show up on xerox machines. As a result, any copies look neat and only show the words, which are meant to be the focus anyway. From a marketing standpoint, though, this also ensures consumers don’t buy a notebook, then xerox copies of lined paper on their own to keep reproducing without buying more notebooks. At best, they would get a blank notebook page with a faint margin.