<style>
.outter {
position: relative;
padding: 5px;
height: 50px;
300px;
}
.outter::before {
position: absolute;
content: '';
height: 10px;
10px;
right: 0;
top: 0;
border-right: 1px solid #00E8FF;
border-top: 1px solid #00E8FF;
}
.outter::after {
position: absolute;
content: '';
height: 10px;
10px;
left: 0;
bottom: 0;
border-left: 1px solid #00E8FF;
border-bottom: 1px solid #00E8FF;
}
.content {
position: relative;
height: 50px;
}
.content::before {
position: absolute;
content: '';
height: 10px;
10px;
left: -5px;
top: -5px;
border-left: 1px solid #00E8FF;
border-top: 1px solid #00E8FF;
}
.content::after {
position: absolute;
content: '';
height: 10px;
10px;
right: -5px;
bottom: 5px;
border-right: 1px solid #00E8FF;
border-bottom: 1px solid #00E8FF;
}
</style>
<div class="outter">
<div class="content">
</div>
</div>