使用 CSS 扩展边框

body {
  margin: 0;
  padding: 0;
  width: 100%;
  font-family: Helvetica, Arial, sans-serif;
  /* text-align: center; */
}

.container {
  margin: 50px auto 0;
  padding: 0;
  width: 75%;
  height: 200px;
  position: relative;
}

.box-vert {
  margin: -10px 0;
  padding: 0;
  overflow: visible;
  height: 200px;
  position: absolute;
  border: 1px solid #C5C5C5;
  border-top: none;
  border-bottom: none;
}

.box-horz {
  height: 180px;
  margin: 10px -10px;
  overflow: visible;
  border: 1px solid #C5C5C5;
  border-left: none;
  border-right: none;
  padding: 0;
}

.box-inner {
  margin: 0 10px;
  padding: 20px;
  background-color: #ECECEC;
  height: 140px;
  float: left;
  overflow: hidden;
}

.box-inner h1 {
  margin: 0 0 10px;
  text-transform: uppercase;
  font-weight: 200;
  letter-spacing: 3px;
  font-size: 30px;
  color: #009688;
}

.box-inner p {
  margin: 0;
  line-height: 1.4;
  font-size: 14px;
  color: #666;
}

<div class="container">
  <div class="box-vert">
    <div class="box-horz">
      <div class="box-inner">
        <h1>Title Text Here</h1>
        <p>Aenean eu leo quam. Pellentesque ornare sem lacinia quam venenatis vestibulum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Cras mattis consectetur purus sit amet fermentum. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vestibulum id ligula porta felis euismod semper.</p>
      </div>
    </div>
  </div>
</div>

div {
  padding: 15px;
  margin-bottom: 10px;
  line-height: 1.4;
  font-size: 14px;
  color: #666;
  background: linear-gradient(#C5C5C5, #C5C5C5), linear-gradient(#C5C5C5, #C5C5C5), linear-gradient(#C5C5C5, #C5C5C5), linear-gradient(#C5C5C5, #C5C5C5), linear-gradient(#ECECEC, #ECECEC);
  background-size: 100% 1px, 1px 100%, 100% 1px, 1px 100%, calc(100% - 20px) calc(100% - 20px);
  background-position: 0px 10px, calc(100% - 10px) 0px, 0px calc(100% - 10px), 10px 0px, 10px 10px;
  background-repeat: no-repeat;
}

/* Just for demo */

h1 {
  margin: 0 0 10px;
  text-transform: uppercase;
  font-weight: 200;
  letter-spacing: 3px;
  font-size: 30px;
  color: #009688;
}
body {
  margin: 0;
  padding: 0;
  width: 100%;
  font-family: Helvetica, Arial, sans-serif;
  /* text-align: center; */
}

<div>
  <h1>Title Text here</h1>
  Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book.</div>

<div>
  <h1>Title Text here</h1>
  Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has
  survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing
  software like Aldus PageMaker including versions of Lorem Ipsum.</div>