border bootstrap
<span class="border border-primary"></span> <span class="border border-secondary"></span> <span class="border border-success"></span> <span class="border border-danger"></span> <span class="border border-warning"></span> <span class="border border-info"></span> <span class="border border-light"></span> <span class="border border-dark"></span> <span class="border border-white"></span> <span class="border-0"></span> <span class="border-top-0"></span> <span class="border-right-0"></span> <span class="border-bottom-0"></span> <span class="border-left-0"></span>