<div class="main">
  <div class="box box1"></div>
  <div class="box box2"></div>
  <div class="box box3"></div>
</div>

.main {
  position: relative;
  width: 500px;
  height: 500px;
  margin: 150px auto;
}

.box {
  position: absolute;
  top: 0;
  left: 0;
  width: 346px;
  height: 200px;
  background-color: red;
  border-left: 1px solid #000;
  border-right: 1px solid #000;
}

.box2 {
  transform: rotate(120deg);
}
.box3 {
  transform: rotate(-120deg);
}