Custom Templates for Google Tag Manager
Custom templates, a new feature recently built into Tag Manager, are potentially great for getting things done in Google's ever useful management tool.
Custom templates allow you to write and use your own definitions for custom tracking solutions not already built into GTM's already fairly comprehensive list of built-in templates you see whenever you set up a new tag or variable. This allows advanced users to write and manage new templates and give permission to less technical users so they can use them as they would built-in tags, without getting their hands dirty with code.
The power in them lies in the use of permissions to strictly control the behaviour of the sandbox API they must use. This means declaring exactly what your custom tags or variables are permitted to do so other users can see.
This is great for larger organisations that want to deploy bespoke tagging functionality without adding loads of extra code to a site - developers can write the new templates and marketers can see exactly what they do and use them when needed.