From Georgetown University Commons Knowledge Base
The "sticky posts" feature allows you to take any post you publish and place it at the top of your public facing homepage without editing the time stamp. It prioritizes this post, filing posts published before and after below. You can access this feature in the Post edit page. On the right-hand side of the screen, in the "Publish" module, there is a "Visibility" category where you can control whether a post is public or private. To prioritize the post, check the "Stick this post to the front page" box. This post will then be pulled to the top of your homepage. To make a post "unsticky" simply uncheck the box.