Simple holder optimized for a typical machinists ruler. This design integrates a 10mm x 3mm circular magnet, and sits flush against a surface with the use of 3M double sided tape.
Use 2 or more of these.
print at 100% infill. magnets can be inserted with a little dab of glue after the print is complete. if you slide your ruler in, they line themselves up and can be stuck in place with no need for other tools.
Magnets that work: https://www.amazon.com/DIYMAG-Refrigerator-Magnets-Premium-Brushed/dp/B08GLS59JS/ref=sr_1_5?crid=2OK34VHMAT1ED&keywords=10mm+x+3mm+magnet&qid=1669586886&sprefix=10mm+x+3mm+magne%2Caps%2C139&sr=8-5
The author hasn't provided the model origin yet.