I use the class border-\* of bootstrap, but can't see the borders.
 1. What am I missing ?
 2. Where do I change the thikness of the border ?
 3. Why there is a silght gap, the white spot between the cells in the outcoume result of the following code ?
 4. I used the class rounded-0 and it still seams to be exists, why ?

Thanks un advance for any help.

```css
div {
height: 50px;
}
```

```html
    <!-- Jquery -->
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
    <!-- BootStrap -->
    <!-- Latest compiled and minified CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
    <!-- Optional theme -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">
    <!-- Latest compiled and minified JavaScript -->
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
    <!-------------------------------------------------------------------------->
    <div class="container-fluid row">
      <h1 class = 'page-header'>
      Why the borders are not visible ?
      </h1>
      <h5>And why the radius box is still rounded if the class is rounded-0 ?</h5>
      <div class='btn btn-primary rounded-0 col-xs-4'></div>
      <div class='btn btn-primary rounded-0 col-xs-4 border-top-0'></div>
      <div class='btn btn-primary rounded-0 col-xs-4 '></div>
      <div class='btn btn-primary rounded-0 col-xs-4 border-left-0'></div>
      <div class='btn btn-primary rounded-0 col-xs-4 '></div>
      <div class='btn btn-primary rounded-0 col-xs-4  border-right-0'></div>
      <div class='btn btn-primary rounded-0 col-xs-4'></div>
      <div class='btn btn-primary rounded-0 col-xs-4 border-bottom-0'></div>
      <div class='btn btn-primary rounded-0 col-xs-4'></div>
     </div>
```