Interesting (and annoying).
If you redirect to your root-path and pass it an anchor tag like "show-help" (in some controller) eg with
redirect_to root_path(:anchor => 'show-help')
It first redirects correctly to /#show-help but it then further redirects to your actual root url... and removes the anchor tag eg /my_dashboard
My expectation would be that it would preserve the anchor tag... eg the final URL would be: /my_dashboard#show-help
But of course, the browser doesn't actually send anchor tags to the server at all... which means that after the first request (to '/'), Rails never gets the anchor tag back again to pass onto the redirected url, which is why it gets dropped.
This is an issue if you really want to open the url with an anchor tag.
The main option you have is to not use root_url, but directly use the actual url you need eg: my_dashboard_url(:anchor => 'show-help'). It's not the best, but at least it works.