# Create a \<hr\> between Plot markers?

**URL:** <https://talk.observablehq.com/t/create-a-hr-between-plot-markers/10221>\
**Category:** Help\
**Created:** [February 2, 2025, 11:22pm UTC](https://talk.observablehq.com/t/create-a-hr-between-plot-markers/10221 "2025-02-02T23:22:51Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Maya](https://yyz2.discourse-cdn.com/flex030/user_avatar/talk.observablehq.com/maya/32/4294_2.png) [@Maya](https://talk.observablehq.com/u/Maya)\
**Post date:** [February 2, 2025, 11:22pm UTC](https://talk.observablehq.com/t/create-a-hr-between-plot-markers/10221/1 "2025-02-02T23:22:51Z")

</div>

Hi everyone! I have a categorical heatmap that I want to add a sort of line break to between two categories - I’ve tried using ruleY but to no avail… How would I make a black horizontal line between “param3” and “Collector Initials” in the following example: [Combining heatmaps / Maya Gans | Observable](https://observablehq.com/d/e69428db4e56302c)

I combined the data but maybe I should really keep these as two separate vectors, then put some kind of spacer between?

I tried this:

```auto
    Plot.ruleY(["Collector Initials"], {
      stroke: 'black',
      strokeWidth: 2
    }),

```

but i essentially want be able to bump this line up/do a transform on it?

I also tried:

```auto
 y: {
    label: null,
    domain: [
  "param1", 
  "param2", 
  "param3", 
 "spacer",
  "Collector Initials",  
  "Time Collected"
];
  },

```

then put the like at “Spacer” but I dont want to see the word spacer or have an axis tick, and it was really thick (the same thickness as other y-axis marks) so i dont love that…

Any thoughts appreciated!!

---

<div class="post-metadata">

**Author:** ![Fil](https://yyz2.discourse-cdn.com/flex030/user_avatar/talk.observablehq.com/fil/32/207_2.png) [@Fil](https://talk.observablehq.com/u/Fil)\
**Post date:** [February 3, 2025, 9:11am UTC](https://talk.observablehq.com/t/create-a-hr-between-plot-markers/10221/2 "2025-02-03T09:11:47Z")

</div>

I’m afraid this is not supported in Plot (and not even in D3 scales). It would be useful though! A new type of ordinal scale that has a tree as domain rather than a list. Note that a similar question was asked in [Grid within plot.cell](https://talk.observablehq.com/t/grid-within-plot-cell/10215)