Creating Template Listeners
From phpBB Development Wiki
What are template hooks?
How to use one
I'm assuming you already know what the ledge's identifer is. If you don't then you should look it up on the Ledges_List. If it isn't on the ledges list you can add it as described in the Adding_Ledges article.
So lets say our ledge is called overall_header_head and injects into overall_header.html in the head element.You create a file in your extension in
You essentially call the file by the ledge identifier followed by .html
Then you type in the content you want to be injected where that ledge is and your good to do. Its as simple as that.
If you want it to work for all styles (recommended) then instead of style name use `all`.