textual/docs/examples/styles/border_subtitle_align.tcss

#label1 {
    border: solid $secondary;
    border-subtitle-align: left;
}

#label2 {
    border: dashed $secondary;
    border-subtitle-align: center;
}

#label3 {
    border: tall $secondary;
    border-subtitle-align: right;
}

Screen > Label {
    width: 100%;
    height: 5;
    content-align: center middle;
    color: white;
    margin: 1;
    box-sizing: border-box;
}