使用边框类添加或删除元素的边框。从所有边框中选择，或者一次选择一个。

增加的

<span class="border"></span>
<span class="border-top"></span>
<span class="border-end"></span>
<span class="border-bottom"></span>
<span class="border-start"></span>

删减的

<span class="border-0"></span>
<span class="border-top-0"></span>
<span class="border-end-0"></span>
<span class="border-bottom-0"></span>
<span class="border-start-0"></span>

边框颜色

使用基于主题颜色构建的类更改边框颜色。

<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>

边框宽度

<span class="border border-1"></span>
<span class="border border-2"></span>
<span class="border border-3"></span>
<span class="border border-4"></span>
<span class="border border-5"></span>

边框圆角

<img src="..." alt="..." class="rounded">
<img src="..." alt="..." class="rounded-top">
<img src="..." alt="..." class="rounded-right">
<img src="..." alt="..." class="rounded-bottom">
<img src="..." alt="..." class="rounded-left">
<img src="..." alt="..." class="rounded-circle">
<img src="..." alt="..." class="rounded-pill">

尺寸

<img src="..." alt="..." class="rounded-0">
<img src="..." alt="..." class="rounded-1">
<img src="..." alt="..." class="rounded-2">
<img src="..." alt="..." class="rounded-3">