How to make a scrollable tool bar fix when reaches top?

Hello all,

I’ve searched the docs and forum, but didn’t found what I need.
I need to create a toolbar that in certain view will appear in middle-bottom on the screen.

As long as the users scrolls and that toolbar reaches the top, it must then be fixed right bellow the header.

This way user won’t need to scroll back to top to change content bellow that toolbar.