.class:after{ content: ‘‘; border-top: 8px solid rgb(233, 221, 221); border-left: 18px solid transparent; border-right: 18px solid transparent; }
主要就是设置border的上和左右值，设置为transparent则是让其透明，则画出一个相应图标
.header-bottom-left{ text-align: center; position: relative; &:after{ position: absolute; content: ‘‘; border-top: 8px solid rgb(233, 221, 221); border-left: 18px solid transparent; border-right: 18px solid transparent; top: 39px; left: 70px; } }
原文：https://www.cnblogs.com/cazj/p/11263048.html