<!DOCTYPE html>
<style>
.test {
  background: green;
  border: solid 2px;
}

.container-1 {
  height: 100px;
  width: 300px;
}

.container-2 {
  height: 50px;
  width: 50px;
}

.container-3 {
  height: 80px;
  width: 80px;
}

.left {
  float: left;
  writing-mode: horizontal-tb;
}

.right {
  float: right;
  writing-mode: vertical-rl;
}
</style>

<div class="container-1">
  <div class="left test" style="height: 100px; width: 96px;"></div>
  <div class="right test" style="height: 96px; width: 100px;"></div>
</div>

<div class="container-2">
  <div class="left test" style="height: 25px; width: 46px;"></div>
  <div class="right test" style="height: 46px; width: 25px;"></div>
</div>

<div class="container-3">
  <div class="left test" style="height: 25px; width: 76px;"></div>
  <div class="right test" style="height: 76px; width: 25px;"></div>
</div>
