<style>
div {
min-height: 150px;
min-width: 150px;
margin: 20px;
display: inline-block;
}
body {
margin-bottom: 500px;
}
</style>
https://getbootstrap.kr/docs/5.1/utilities/borders/
<!-- ADDING BORDERS -->
<div class="border"></div>
<div class="border-top"></div>
<div class="border-bottom"></div>
<div class="border-start"></div>
<div class="border-end"></div>
<div class="border-end border-start border-top"></div>
<br>
<!-- REMOVING BORDERS -->
<div class="border border-top-0"></div>
<div class="border border-bottom-0"></div>
<div class="border border-start-0"></div>
<div class="border border-end-0"></div>
<br>
<!-- BORDER WIDTH -->
<div class="border border-1"></div>
<div class="border border-2"></div>
<div class="border border-3"></div>
<div class="border border-4"></div>
<div class="border border-5"></div>
<br>
<!-- BORDER COLORS -->
<div class="border border-5 border-primary"></div>
<div class="border border-5 border-secondary"></div>
<div class="border border-5 border-success"></div>
<div class="border border-5 border-danger"></div>
<div class="border border-5 border-warning"></div>
<div class="border border-5 border-info"></div>
<div class="border border-5 border-light"></div>
<div class="border border-5 border-dark"></div>
<div class="border border-5 border-white"></div>
<br>
<!-- BORDER RADIUS -->
<div class="border rounded"></div>
<div class="border rounded-top"></div>
<div class="border rounded-bottom"></div>
<div class="border rounded-start"></div>
<div class="border rounded-end"></div>
<div class="border rounded-circle"></div>
<div style="width: 400px;" class="border rounded-pill"></div>
<!-- ROUNDED SIZES -->
<div class="border rounded-1"></div>
<div class="border rounded-2"></div>
<div class="border rounded-3"></div>
<div class="border rounded-0"></div>