Where to place new slips - Zettelkasten

by Alex Nelson, 14 July 2026

This is a common problem people face when getting started with a Zettelkasten: I have just written notes on slips, and I do not know where to place them (or, equivalently, I do not know what ID numbers to put on them). What do I do?

Perhaps it is best to work by example.

Example

Background setting: I mentioned in my note on getting started that I tend to make the first “section” in my Zettelkasten about Zettelkastens in general, and the decisions I have made concerning my Zettelkasten.

To review the “minimal” Zettelkasten, the slips are:

• 1. Zettelkasten The idea of Zettelkasten as some kind of method for taking notes
  • 1/1 Slips The basic constituent of a Zettelkasten is the slip of paper. Without this, there is literally no Zettelkasten.
  • 1/2 Links Referencing other ideas in the Zettelkasten is how we form relations between ideas. Relations are how we can generate new ideas.

    • 1/2a Branches Sometimes I want to expand on something said in a slip. In these cases, I write (a), (b), (c), …, (z) in red ink, and then append (correspondingly) a, b, …, z to the ID number to form a “branch”. For example, 1/2a is a branch off 1/2.

      If I had more to say about branches, I would modify the ID number for branches to be 1/2a1 Branches. The next slip in this train of thought would have ID number 1/2a2, then 1/2a3, then 1/2a4, and so on.

    • 1/2b Red Ink for Links I realized it is more striking visually to use red ink for links — I just write the ID number in parentheses in red ink. (Initially, I tried using blank ink, and I later changed conventions.)

  • 1/3 Bibliography notes I take notes while reading books. These reading notes (or “Bibliography notes”) go in a separate shoe box. I form “permanent notes” which go in the Zettelkasten from the “Bibliography notes”.

    Importantly: Bibliography notes contain all the information necessary for me to cite the article (or book or website or preprint or…). I typically write this on one side of the reading notes (as well as the date I read it).

    My “bibliography shoe box” is organized by author-date-title (and if necessary, the date I read the material—sometimes I re-read the same article multiple times, in different contexts).

  • 1/4 Workflow How do I actually, you know, “do stuff”? This includes (a) populating the Zettelkasten with new slips, and (b) use these slips to…do stuff. (Those two items were actually branches, did you notice?)
    • 1/4a1 Growing a Zettelkasten Adding new notes to a Zettelkasten involves reading material, thinking about stuff, writing it down, assigning an ID number, then placing it in the shoe box.
    • 1/4a2 Lecture notes Thoughts about how to integrate lecture notes into the Zettelkasten. I ultimately decided to treat lecture notes as an unpublished manuscript which I can reference without requiring any corresponding “bibliography note”.
    • 1/4b1 Using a Zettelkasten I am certain there are multiple ways to use a Zettelkasten. For myself (as for Luhmann), I am using it to write articles and books and things.
  • 1/5 Organization Discussion about how to organize the slips in my Zettelkasten.
    • 1/5a ID Numbers The numbering scheme I am using (which came from a misunderstanding of Luhmann)
    • 1/5b1 Sections Clustering discussions into “sections” makes sense for my Zettelkasten. But I create sections as I need them as opposed to “prepopulating” my Zettelkasten with sections.

    • 1/5b2 Subsection I realize that Luhmann is using the really old-school Tractatus-style numbering scheme where 1.1/ is a section and 1.11 is the first subsection of 1.1 — we don’t do this anymore. Instead we would add a period 1.1.1. I’m going to follow this sensible modern convention.

      Furthermore, I will try to resist adding “too many” sub-…-subsections.

So far, so good, right?

New slips: I am interested in using fountain pens when writing on the slips for my Zettelkasten, which got me thinking about the difference between ballpoint pens vs rollball pens vs gel pens, and how do fountain pens work?

This leads me to introduce the new slips about:

• Ballpoint ink
• Rollerball ink
• Gel ink
• Archival quality ink
• Paper production
• Acid-free paper
• Storing paper

Where do I place all these notes? It does not matter. To demonstrate this point, I can offer several different places where they are inserted.

Possible solutions

To review (for “ease of reference”) here is the Zettelkasten before inserting anything:

• 1. Zettelkasten
  • 1/1 Slips
  • 1/2 Links
    • 1/2a Branches
    • 1/2b Red Ink for Links
  • 1/3 Bibliography notes
  • 1/4 Workflow
    • 1/4a1 Growing a Zettelkasten
    • 1/4a2 Lecture notes
    • 1/4b1 Using a Zettelkasten
  • 1/5 Organization
    • 1/5a ID Numbers
    • 1/5b1 Sections
    • 1/5b2 Subsection

Solution 1: Ink with ink, paper with slips

One possibility is to:

1. insert the train of thought about “inks” as a branch off the slip 1/2b1 Red Ink for Links since it’s also talking about ink
2. insert the train of thought about “paper” as a branch off 1/1 Slips

• 1. Zettelkasten
  • 1/1 Slips
    • NEW 1/1a1 Paper production
    • NEW 1/1a2 Acid-free paper
    • NEW 1/1a3 Storing paper
  • 1/2 Links
    • 1/2a Branches
    • 1/2b1 Red Ink for Links
      • NEW 1/2b1a1 Ballpoint ink
      • NEW 1/2b1a2 Rollerball ink
      • NEW 1/2b1a3 Gel ink
      • NEW 1/2b1a4 Archival quality ink
  • 1/3 Bibliography notes
  • 1/4 Workflow
    • 1/4a1 Growing a Zettelkasten
    • 1/4a2 Lecture notes
    • 1/4b1 Using a Zettelkasten
  • 1/5 Organization
    • 1/5a ID Numbers
    • 1/5b1 Sections
    • 1/5b2 Subsection

Solution 2: As branches off “slips”

Since, in 1/1 Slips I am talking about writing notes with ink on paper, both trains of thought could be inserted there as branches.

• 1. Zettelkasten
  • 1/1 Slips
    • NEW 1/1a1 Paper production
    • NEW 1/1a2 Acid-free paper
    • NEW 1/1a3 Storing paper
    • NEW 1/1b1 Ballpoint ink
    • NEW 1/1b2 Rollerball ink
    • NEW 1/1b3 Gel ink
    • NEW 1/1b4 Archival quality ink
  • 1/2 Links
    • 1/2a Branches
    • 1/2b1 Red Ink for Links
  • 1/3 Bibliography notes
  • 1/4 Workflow
    • 1/4a1 Growing a Zettelkasten
    • 1/4a2 Lecture notes
    • 1/4b1 Using a Zettelkasten
  • 1/5 Organization
    • 1/5a ID Numbers
    • 1/5b1 Sections
    • 1/5b2 Subsection

Solution 3: As branches off “Workflow”

Since I am speaking about working with paper and pen in 1/4 Workflow, I could easily add more slips as a branch off the discussion of “paper” and “pen” appearing on that slip, so the resulting Zettelkasten looks like:

• 1. Zettelkasten
  • 1/1 Slips
  • 1/2 Links
    • 1/2a Branches
    • 1/2b1 Red Ink for Links
  • 1/3 Bibliography notes
  • 1/4 Workflow
    • 1/4a1 Growing a Zettelkasten
    • 1/4a2 Lecture notes
    • 1/4b1 Using a Zettelkasten
    • NEW 1/4c1 Paper production
    • NEW 1/4c2 Acid-free paper
    • NEW 1/4c3 Storing paper
    • NEW 1/4d1 Ballpoint ink
    • NEW 1/4d2 Rollerball ink
    • NEW 1/4d3 Gel ink
    • NEW 1/4d4 Archival quality ink
  • 1/5 Organization
    • 1/5a ID Numbers
    • 1/5b1 Sections
    • 1/5b2 Subsection

But what’s “the right answer”?

As I said, it does not matter. What matters is that I form links with existing concepts and integrate them into the Zettelkasten.

If it turns out, later, there was a “better” place to insert the slips about “paper” — then all I have to do is link to the train of thought about paper. That’s it. That’s the power of links.

If I were to develop more thoughts about paper (or ink, or pens, or…), then I would continue to develop the train of thought.

For the sake of argument, let us suppose I “forgot” I had written about the different types of inks. Suppose I were inserting notes about different writing instruments and their possible longevity for archival puposes (because I am going to visit an archive and I need to be mindful about these things).

Suppose I then have a completely different train of thought in a different section, to record my knowledge about this stuff. For example:

• 2.1. Archives
  • 2.1/1 Archival quality paper
    • 2.1/1a1 Non-archival quality paper
    • 2.1/1a2 Paper production process
    • 2.1/1a3 Printer paper
  • 2.1/2 Archival quality inks
  • 2.1/3 Pencils and archives

Then after returning from backbreaking labour in the salt mines archives, I realize I have duplicated the discussion about “archival quality paper”. Oh no! What do I do?

Well, I can add links on the “Paper train of thought” in the 1. Zettelkasten section referring to the 2.1/1 slip and its branching trains of thought. Then I add links from the 1. Zettelkasten paper discussions onto the slips appearing in 2.1/1 Archival quality paper (and relevant branches). This way, I have references to different parts of the Zettelkasten when the same subject accidentally was entered twice.

One advantage to this is that I can continue to develop my knowledge about archival practices independent of my observations about Zettelkastens, since they are two independent subjects. But they also feedback into each other (at least, archival practices feeds into Zettelkasten workflow practices) because I am concerned about my notes accidentally being lost from bad paper quality, or acidity in the ink destroying the paper, or…some other unforeseeable situation!

This is an advantage because I can continue to develop my notes about archives without panicking about where to place things in my Zettelkasten.

But I should also look at this as an opportunity to reflect: how was it even possible for me to enter duplicate notes into the Zettelkasten? Something in my workflow failed to catch this. What could I have done to have avoided this situation? Is this even a problem?

When things “break down” in the Zettelkasten work flow, it is an opportunity to reflect, examine your practices, and experiment on ways to avoid it in the future.