custom header.php question

I found a tutorial for adding a widget area to the header of the twenty twelve theme. – yes I am using a child theme – I’ve followed the first two steps, register a widget area in the header, via the functions.php, and added code to make it work in a new file called sidebar-header.php (I’ve already uploaded that).

The final line of code that the tutorial says to add is this:

<?php get_sidebar( 'header' ); ?>

The tutorial says to add that code to the custom header.php file (in your child theme of course). My question is, does that guy mean the header.php file or the custom-header.php file? The way he has it worded on his tutorial makes it unclear about which file he means because it could mean your custom header that you are making. Or at least that is where I’m unsure.