Add to template hook

[Dragonsys]

I am trying to merge a custom template, into another existing template by using a plugin. I have the template hook, I'm just not sure how to get my plugin to add to the data which is already in the hook. Most of what I have found by searching deals with older version of VB 3.8 while I am working with 4.2.

EDIT: I found it

$template_hook['hook_name'] .= '{code}';