<nav class="nav nav-pills flex-column flex-sm-row">
<a class="flex-sm-fill text-sm-center nav-link active" href="#">Active</a>
<a class="flex-sm-fill text-sm-center nav-link" href="#">Link</a>
<a class="flex-sm-fill text-sm-center nav-link" href="#">Link</a>
</nav>
You don't need to remember all CSS classes. Just use the Bootstrap Editor instead.