Vertical space when stacking columns in Bootstrap 3

Question

One way would be with CSS that adds margin-bottom to col-* on smaller devices/widths..

@media (max-width: 768px) {

  [class*="col-"] {
      margin-bottom: 15px;
  }

}

Another way is to add a div that is only visible on smaller devices/widths..

 <div class="col-sm-6">
    <div class="hidden-lg hidden-md hidden-sm">&nbsp;</div>
        ...

Demo: http://bootply.com/92276

Update 2019

Bootstrap 4 now has spacing utilities that can be used.

Also see: Add spacing between vertically stacked columns in Bootstrap 4