[TYPO3] include basis template?

[Aleksandar Milovac]

Hi,

I want to make some of the TS code that I've been using modular and use
it on different sites. For example, TS code used to generate menu can be
included as a basis template.
Does this file(basis template) have to be in some special format or I
can leave it as a simple txt file. How to include this file later in a
site? I mean where do I upload it?

Thanks,
Aleksandar