How to use a custom template

[mccollin]

I can create a custom template in the admin cp, but how do I call it in another template. I've expanded some of the standard templates to the point that I'd really like to break them up. As an example, I have a header template that has several banners and custom menus in it. In order to faciliate changing the things that change, without accidentally breaking the tables, I'd like to create a "headerbanner" template and a "header menu" template and then call them in the header template. I can create new ones, but when I place them in the header template, they don't get resolved. Could someone explain this please?

(I've just moved to vB a few weeks ago after heavily modifying a phpBB based system, so I'm a novice at vB, but can handle a technical explanation)