I wanted to make a horizontal line extend across the column width specified by the bootstrap parent element. I am using Bootstrap 4.1.1. the code is as follows.

```
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-WskhaSGFgHYWDcbwN70/dfYBj47jz9qbsMId/iRN3ewGhXQFZCSftd1LZCfmhktB" crossorigin="anonymous">
<div class="row">
    <div class="col-xs-5">
        <p>Something here!</p>
        <hr/>
        <p>This list!</p>
    </div>
</div>

```

The `<hr>` tag inherits parent `<div>` property and that prevents the `<hr>` tag to extend up to the length of the bootstrap's container class.

js fiddle here:
<https://jsfiddle.net/7gu21n8z/>