Update on 9/17:

After using the original model for some time I realized eventually the clip loosens up and the phone mount becomes less sturdy. 

As a result, I created a newer design with a twist-fit mechanism that allows the phone mount to lock into a profile rail directly.

There are two print profiles labeled vertical or horizontal - make sure you print the correct one!

The vertical one can be used to lock the phone holder into a vertical rail, and the horizontal one is oriented for a horizontal rail.

To install, simply insert the clip on the back of the phone holder into the rail at a 90 degree angle, and rotate it 90 degrees so that is locks in place and is properly oriented. To remove, rotate it 90 degrees either left or right and it should come out of the rail easily.

I have tested both only on my Sim Lab GT1 Evo, but I believe these should work for many other standard aluminum profile rigs as well.

Original description:

I modified this racing seat style phone holder to be mountable onto my Sim-Lab GT1 Evo sim racing rig. It slides easily into a groove on top of any rail at a slight angle so that your phone will remain upright without bumping into the rig itself. Hope you find this useful!