hugo-theme-paradox/layouts/partials/styles/borders.html

<style>
.site-header {
	border-bottom: 1px solid;
	border-color: var(--ui-border, rgba(0,0,0,0));
	transition: border-color var(--color-crossfade-duration) var(--color-crossfade-ease);
}
.site-footer {
	border-top: 1px solid;
	border-color: var(--ui-border, rgba(0,0,0,0));
	transition: border-color var(--color-crossfade-duration) var(--color-crossfade-ease);
}
@media (min-width: 60rem) {
	.docs-nav {
		border-right: 1px solid;
		border-color: var(--ui-border, rgba(0,0,0,0));
		transition: border-color var(--color-crossfade-duration) var(--color-crossfade-ease);
	}
}
@media (min-width: 75rem) {
	.toc {
		border-left: 1px solid;
		border-color: var(--ui-border, rgba(0,0,0,0));
		transition: border-color var(--color-crossfade-duration) var(--color-crossfade-ease);
	}
}
</style>