You want to stick a post inside a thread, right? You would have to modify the code quite a bit if you are hoping to be able to just pick one of the posts within the thread and make it 'stick' as the first post. The posts are ordered by the criteria in your User CP when the query to grab them is performed. Usually this is by date ascending or descending. If you want to 'easily' stick a thread at the beginning, you should change the date of the post so it would be the first post in the thread.