Link to Flask static files with url_for

How do you use url_for in Flask to reference a file in a folder? For example, I have some static files in the static folder, some of which may be in subfolders such as static/bootstrap.

When I try to serve a file from static/bootstrap, I get an error.

 <link rel=stylesheet type=text/css href="{{ url_for('static/bootstrap', filename='bootstrap.min.css') }}">

I can reference files that aren't in subfolders with this, which works.

 <link rel=stylesheet type=text/css href="{{ url_for('static', filename='bootstrap.min.css') }}">

What is the correct way to reference static files with url_for? How do I use url_for to generate urls to static files at any level?