<table>
  <tr><td>Колонка 1</td><td>Колонка 2</td><td>Колонка 3</td></tr>
      <tr><td>1</td><td>2</td><td>3</td></tr>
      <tr><td>4</td><td>5</td><td>6</td></tr>
      <tr><td>7</td><td>8</td><td>9</td></tr>
</table>

table {
  position: relative;
  border-collapse: collapse;
}
td {
  padding: 5px;
}
tr:not(:first-child):after {
  content: "";
  position: absolute;
  display: block;
  background: red;
  height: 2px;
  left: 12%;
  right: 12%;
}