Footer Zero creates a fixed container on the bottom of the page that will fade or slide-in (using the animation option) after a given amount of page scroll. This is a widely used stack here at Archetypon: every theme page has a Footer Zero displaying demo links and purchase buttons on the bottom of the page.
We may add any kind of content to the stack, from text to html, images and videos. Footer Zero is developed for Stacks 3 plugin, so it requires RapidWeaver 6 and Stacks 3.
Yep that's Footer Zero!
This stack is widely used here in this website, browse to any theme page and you will find it displaying demo link and purchase buttons at the bottom of the pages.