This simple model was designed as a flip-up flap that blocks a motion-activated light switch for my printer cabinet lights.  Flipping the flap up and down triggers the sensor, turning the lights on and off, rather than waving my hand in front of the sensor (which kept triggering when I would work in the cabinet).

The model is designed for a round 8mm diameter x 3mm thick magnet.  The Fusion file contains favorite parameters to easily adjust the design for other sizes of magnets, different flap sizes, or different distances from the wall this attaches to.  Minimum wall clearance for the flap is approximately 7mm. 

Use a short piece of filament as your hinge pin.  (I used PETG, as PLA can become brittle and break over time.)

What anyone else will use this for..?  No clue.  But I'd love to see if you end up using it.  Post your makes!