<style>
.my_box{ 
position: relative;
margin:8px;
width:80px;
height: 80px;
padding:10px;
background-color: #f1f1f1;
}</style> 

Border of different sides

<div class='my_box border'>All</div> 
<div class='my_box border-top'>Top</div>
<div class='my_box border-right'>Right</div>
<div class='my_box border-bottom'>Bottom</div>
<div class='my_box border-bottom'>Left</div>

Remove Borders

<div class='my_box border border-0'>All</div> 
<div class='my_box border border-top-0'>Top</div>
<div class='my_box border border-right-0'>Right</div>
<div class='my_box border border-bottom-0'>Bottom</div>
<div class='my_box border border-bottom-0'>Left</div>

Border Colour

<div class='my_box border border-primary'>primary</div> 
<div class='my_box border border-secondary'>secondary</div>
<div class='my_box border border-success'>success</div>
<div class='my_box border border-danger'>danger</div>
<div class='my_box border border-warning'>warning</div>
<div class='my_box border border-info'>info</div>
<div class='my_box border border-dark'>dark</div>
<div class='my_box border border-light'>light</div>
<div class='my_box border border-white'>white</div>

Rounded corners border

<div class='my_box rounded'>All</div> 
<div class='my_box rounded-top'>top</div> 
<div class='my_box rounded-right'>right</div>
<div class='my_box rounded-bottom'>bottom</div>
<div class='my_box rounded-left'>left</div> 
<div class='my_box rounded-circle'>circle</div> 
<div class='my_box rounded-0'>0</div>