This is a hanger for two accessories for the Vitruvian Form Trainer+ on a Rubbermaid Fasttrack rail. The accessories won't rub on the wall, and you can hang two like-accessories up at once (both handles, cables, etc.)
Print on its side with supports for the channel. The supports were easy to remove even in PETG in my experience.
This is a remix of dhulihan's clip here: https://www.thingiverse.com/thing:166941
The author remixed this model.