10px solid black;
  line-height: 0;
  padding: 0;
}

span {
  display: inline-block;
  width: 10px;
  height: 10px;
  background: grey;
}

.spacer-1 {
  height: 2px;
}

.spacer-2 {
  height: 5px;
}

.spacer-3 {
  height: 10px;
}
</style>
<!-- Empty rows -->
<table>
<tr><td><span></span></td><td><span></span></td></tr>
<tr></tr>
<tr><td><span></span></td><td><span></span></td></tr>
<tr></tr>
<tr><td><span></span></td><td><span></span></td></tr>
<tr></tr>
<tr><td><span></span></td><td><span></span></td></tr>
