Both, with the jack placed depending on what I want to lift. If I want to lift a whole side of the I place the jack in the middle of the rail. If I am lifting a corner I move it accordingly. Just be sure to use a jack pad to avoid scratching the finish off the rails to prevent rust.

 

These are continuing to be a great seller ... happy to help with a set!

https://www.steeda.com/steeda-s197-m...ing-rails.html