public function save_post( $post_id ) {

		if (
			empty( $_POST['rock-layout-nonce'] )
			||
			! wp_verify_nonce( $_POST['rock-layout-nonce'], basename( __FILE__ ) )
		) {

			return;

		}

		$override = ! empty( $_POST['rock-layout-override'] );
		$current  = $this->get_post_layout( $post_id );

		if ( ! $override && $current ) {

			delete_post_meta( $post_id, 'rock_layout' );

			return;

		}

		$layout = isset( $_POST['rock-layout'] ) ? sanitize_key( $_POST['rock-layout'] ) : null;

		if ( ! $override || ! $this->layout_exists( $layout ) || $layout === $current ) {

			return;

		}

		update_post_meta( $post_id, 'rock_layout', $layout );

	}