Código HTML:
<!DOCTYPE HTML>
<html lang="es">
<head>
<style>
.fieldset {
border: 2px groove threedface;
border-top: none;
padding: 0.5em;
margin: 1em 2px;
}
.fieldset > h1 {
font: 1em normal;
margin: -1em -0.5em 0;
}
.fieldset > h1 > span {
float: left;
}
.fieldset > h1:before {
border-top: 2px groove threedface;
content: ' ';
float: left;
margin: 0.5em 2px 0 -1px;
width: 0.75em;
}
.fieldset > h1:after {
border-top: 2px groove threedface;
content: ' ';
display: block;
height: 1.5em;
left: 2px;
margin: 0 1px 0 0;
overflow: hidden;
position: relative;
top: 0.5em;
}
</style>
</head>
<body>
<div class="fieldset"><h1><span>Legend</span></h1> Fieldset</div>
</body>