Custom Menu and bx_injection

I am removing the top menu and replacing it with a custom menu with pretty buttons.  I am curious about the bx_injections tags I see in the _sub_header.html file that are before and after the top menu key.

<bx_injection:injection_between_logo_top_menu />

<bx_injection:injection_between_top_menu_content />

They are of the form of self-closing html tags.  What is the function of these tags?  What does these tags do?

Modules can inject something here.

By default they are not used, but some 3rd-party modules can use it.

I see, they are similar to what we call "hooks" on the CMS proggy that I am helping to develop.  Mmm, I might could use them then.  Is there a developer guide somewhere I could read to learn more?

Developer guide? Not really. Dolphin has never been very big on documentation.

I use them in a few of my newer modules.

The instructions are in the file inc/classes/BxDolTemplate.php

 * Add injection:
 *  1. Register it in the `sys_injections` table or `sys_injections_admin` table for admin panel.
 *  2. Clear injections cache(sys_injections.inc and sys_injections_admin.inc in cache folder).


They are actually template keys. Those that start with the word injection are predefined and are handled by dolphin and are placed in the database table i mentioned above. And those work from within any dolphin template.

The rest start and end with two underscores __

Those are not global like the injections. Processed by the specific php scripts that use and parse the template.

Example of use is in inc/classes/BxDolTemplate.php

I'm trying to place a paypal donate button directly below my join & login buttons, which are generically placed at the top-right on the homepage using the default template. This _sub_header.html file seems to be the place to do it. I tried placing the paypal button near the injection_logo_after section of the _sub_header.html file and that doesn't work the way I am seeking. The button becomes placed below the header. I have been trying to figure this out all day. Please, if you know how to get the button placed directly below the join/login (top-right of the homepage), please explain. Thank you! :)