Question: I am using `Bootstrap` and I want add a button at right of a bar that looks like `<input-group-addon>`. To be specific, full height and locates at right most.

I've tried `height: 100%` but the button styles super high.

this is part of my code: <https://plnkr.co/edit/lK8vt0wT1xDesuOZW8vU?p=preview>

this is what I m looking for [![enter image description here](https://i.stack.imgur.com/TjhI7.png)](https://i.stack.imgur.com/TjhI7.png)

Answer: 
The parent needs `position:relative`.
Then you can position the button absolutely in the corner with `height:100%`

```css
.panel-heading{
  position:relative;
}

button.btn{
  float: none;
  margin-right: 0;
  position: absolute;
  top: 0;
  right: 0;
  height: 100%;
}
```

```html
    <link rel="stylesheet" href="style.css">
    <script src="script.js"></script>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
  </head>

  <body>
    <div class="panel panel-default">
      <div class="panel-heading">Assist Panel<button style="float:right;margin-right:0;" class="btn" onclick="assist_close()"><i class="fa fa-chevron-left"></i></button></div>
      <div class="panel-body"></div>
    </div>
  </body>
```
**Using Position Property** 

```css
.panel-heading{
  position: relative;
}
button.btn{
  position: absolute;
  top:0;
  bottom:0;
  border-radius: 0;
  right: 0;
}
```

```html
<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet"/>
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
 <div class="panel panel-default">
      <div class="panel-heading">Assist Panel<button class="btn" onclick="assist_close()"><i class="fa fa-chevron-left"></i></button></div>
      <div class="panel-body"></div>
    </div>
```