Just like views, layouts can also have helpers on a per-layout, per-layout-folder or per-application basis. If the framework detects the helper, it will inject it into the rendering layout so you can use methods, properties or whatever. All you need to do is follow a set of conventions. Let's say we have a layout in the following location:
Then we can create the following templates
mainHelper.cfm : Helper for the main.cfm layout.
generalHelper.cfm : Helper for any layout in the general folder.
That's it. Just append Helper to the layout or folder name and there you go, the framework will use it as a helper for that layout specifically.
Caution Please note that layout helpers will be inheritenly available to any view rendered inside of the layout.
You can also use the coldbox.viewsHelper directive to tell the framework what helper file to use for ALL layouts rendered: