border bottom 2px in bootstrap code example
Example 1: outline text bootstrap
<span class="border">Text</span>
<span class="border-top">Text</span>
<span class="border-right">Text</span>
<span class="border-bottom">Text</span>
<span class="border-left">Text</span>
Example 2: border bottom class in bootstrap 4
<span class="border"></span>
<span class="border-top"></span>
<span class="border-right"></span>
<span class="border-bottom"></span>
<span class="border-left"></span>