JSFiddle - React, Tailwind, and code Playground

HTML

<div>line 1</div>
<div>line 2</div>
<div class="bigborder"></div>
<div>line 3</div>
<div class="bigborder"></div>
<div class="hidden">line 4</div>
<div class="hidden">line 5</div>
<div class="hidden">line 6</div>
<div class="bigborder"></div>
<div>line 7</div>
<div class="bigborder"></div>
<div>line 8</div>
<div>line 9</div>
<div class="bigborder"></div>
<div>line 10</div>
<div class="bigborder"></div>
<div>line 11</div>
<div>line 12</div>

CSS

div {
    border: 1px solid #AAAAAA;
    padding: 5px;
}
.hidden {
    display: none;
}
.bigborder {
    height: 3px;
    background-color: #AAAAAA;
    margin-top: -3px;
    padding-top: 0;
    padding-bottom: 0;
    border-top-width: 0;
    border-bottom-width: 0;
}