# Scroll Rail Ads

Source: https://docs.ezoic.com/docs/ezoicadsadvanced/scroll-rail/


A scroll rail is a column of display ads that fills a tall sidebar container on desktop. Ads load as the reader scrolls, so the rail stays lightweight on long pages.

Pass the id of one of your own container elements to `ezstandalone.showScrollRail` and Ezoic mounts the rail inside it. The rail is added after any content already in the container and never overlays or repositions your content.

## Usage

```html
<div id="right-sidebar">
    <!-- your sidebar content -->
</div>

<script>
    window.ezstandalone = window.ezstandalone || {};
    ezstandalone.cmd = ezstandalone.cmd || [];
    ezstandalone.cmd.push(function () {
        ezstandalone.showScrollRail('right-sidebar');
    });
</script>
```

The argument is the element's id as a plain string — no `#` prefix. The element must be on the page when you call it.

## Requirements

- **Desktop only.**
- **At least 250px wide.** Make it 300px or wider to allow larger ad sizes (300x600).
- **At least ~1500px tall.** That's enough room for one ad; taller containers get more.

If the container is too narrow or too short, nothing is rendered.

## How Many Ads Appear

One ad per ~1500px of container height:

| Container height | Ads |
|---|---|
| 3,000px | 2 |
| 7,500px | 5 |
| 15,000px | 10 |

Height is measured from below any existing content in your container down to the end of the page content — a container taller than the page itself won't yield more ads.

## Multiple Rails on One Page

Call `showScrollRail` once per container:

```js
ezstandalone.cmd.push(function () {
    ezstandalone.showScrollRail('left-sidebar');
    ezstandalone.showScrollRail('right-sidebar');
});
```

Each rail sizes itself to its own container. Rails are set up in the order they are created.

## Single-Page Apps

The rail automatically re-initializes into the same container id on each new pageview. If a route uses a different container element, call `showScrollRail` again with the new id after the navigation.