I run quite often and walk on the treadmill at home. There is room for a tablet or laptop, but it moves a lot when running. I was looking for a solution so that I could attach the laptop to the wall. I created, printed and assigned my personal solution to the problem.

The holder is needed in two pieces. In the places for the hinges (they are printed together) there is 100% material filling. I printed from PETG.

Minimum slope: 18º (cannot be set horizontally) in the photos an example of the minimum and maximum slope
Maximum slope: 42º
The width is given by the attachment to the wall
Maximum laptop depth: 26 cm

Built primarily for the Macbook Air 2020

Needed: 6 pcs M3x6mm plastic nuts
6 pcs M3x10mm straight head screw

Of course dowels, wall screws again with a straight head.

UPDATE

I added the STL files for the rubbers. These rubbers are suitable if you do not hit the exact height. If one holder is lower, it can be adjusted through the TPU rubber.