What is thold_draw_vrules?

[kjstech]

I can clearly see what hrules are but what is thold_draw_vrules?

On any graph load in the tree, the apache2/error.log spits out this line:
PHP Notice: Undefined index: thold_draw_vrules in /var/www/cacti/plugins/thold/setup.php on line 176, referer: http://intranet/cacti/graph_view.php?ac ... hyper=true

I do not see anything affecting my use of thold though. Is it safe to ignore? I just did a git pull origin master under /thold and it updated a few files after stashing those that were patched manually a few days ago, but still I get this PHP error.