title: How to space vertically stacked buttons in Bootstrap 3
body: <p>I want to have 3 buttons across a row in Bootstrap 3, but when it changes to the xs grid, stack them vertically. I'd like to introduce some spacing (margin) between the buttons - but only when the buttons are stacked vertically. Can I do this in LESS?</p>
  
  <pre><code>          &lt;div class="row"&gt;
              &lt;div class="col-sm-4 btn-vert-block"&gt;
                &lt;span&gt;
                  &lt;button type="button" class="btn btn-primary btn-block"&gt;Go Back&lt;/button&gt;
                &lt;/span&gt;
              &lt;/div&gt;
              &lt;div class="col-sm-4 btn-vert-block"&gt;
                &lt;span&gt;
                  &lt;button type="button" class="btn btn-primary btn-block center-block"&gt;Preview&lt;/button&gt;
                &lt;/span&gt;
              &lt;/div&gt;
              &lt;div class="col-sm-4 btn-vert-block"&gt;
                &lt;span class=""&gt;
                  &lt;button type="button" class="btn btn-success pull-right btn-block"&gt;Go Next&lt;/button&gt;
                &lt;/span&gt;
              &lt;/div&gt;
            &lt;/div&gt;
  </code></pre>