How to Use the RateFast Dual Inclinometer Posted September 3, 2015, updated onMay 19, 2021 by Arun Croll Are you not sure how to use the RateFast Dual Inclinometer mobile app? then you’ve come to the right place. If you have more questions, contact us on Facebook or via email, or call us at 707.304.5949. Try RateFast Express today!