Fieldset

<form>
    <fieldset class="govuk-fieldset">
        <legend class="govuk-fieldset__legend govuk-fieldset__legend--xl">
            <h1 class="govuk-fieldset__heading">
                Fieldset title
            </h1>
        </legend>
        <div class="govuk-form-group">
            <label class="govuk-label" for="user_name">Name</label>
            <input class="govuk-input" type="text" name="user[name]" id="user_name">
        </div>
        <div class="govuk-form-group">
            <label class="govuk-label" for="user_email">Email address</label>
            <input class="govuk-input" type="text" name="user[email]" id="user_email">
        </div>
        <div class="govuk-form-group">
            <input type="submit" name="commit" value="Add new user" aria-label="Add new user" class="govuk-button" data-disable-with="Add new user">
        </div>
    </fieldset>
</form>