タイトル下の誘導線

h2 {
    position: relative;
    padding: 0.5rem 0;
    margin-bottom: 0.2rem;
    border-bottom: 5px solid;
    color: black;
    font-weight: bold;
    font-size: 26px;
}

h2:before,
h2:after {
    position: absolute;
    top: 100%;
    left: 50%;
    content: "";
    height: 0;
    width: 0;
}

h2:before {
    border: 16px solid;
    border-color: transparent;
    border-top-color: black;
    margin-left: -16px;
}

h2:after {
    border: 10px solid;
    border-color: transparent;
    border-top-color: white;
    margin-left: -10px;
}