BTW link to RBI Dividers on Rich Page... Note that He is making them only for his 30/32 qt tube rack...
http://www.reptilebasics.com/rack-systems-for-mid-sized-snakes/mcb-l-tub-divider/
and for practical note.. Dividers first then Substrate is You Using anything different than paper.. otherwise Good Luck with Closing tube lolz...