Add border-bottom to table row <tr>

I had a problem like this before. I don't think tr can take a border styling directly. My workaround was to style the tds in the row:

<tr class="border_bottom">

CSS:

tr.border_bottom td {
  border-bottom: 1px solid black;
}

Use border-collapse:collapse on table and border-bottom: 1pt solid black; on the tr

Add border-collapse:collapse to your table rule:

table { 
    border-collapse: collapse; 
}

Example

table {
  border-collapse: collapse;
}

tr {
  border-bottom: 1pt solid black;
}

<table>
  <tr><td>A1</td><td>B1</td><td>C1</td></tr>
  <tr><td>A2</td><td>B2</td><td>C2</td></tr>
  <tr><td>A2</td><td>B2</td><td>C2</td></tr>
</table>

Link