I am not a 3d modeler by any means, but this is a simple adaptation I made for a threadboard A1 Hotend holder. I used 6mm magnets that are cheap on amazon. This can be horizontal or vertical. Holds the hotends very nicely. I included 2 screws as well that are not as large as the standard threadboard screws for fit. Magnet hole is tight fit I did not need to glue.